Let’s look at important things here –
Sun - Sun represents Personality, King, Government, Father, Authority, Career, Top Positions, Ego, Self Esteem, Health, Education etc.
Uttara Ashadha Nakshatra - It is a nakshatra of career driven people. People who look for authority in life and are highly ambitious. Please check this link to get more information on Uttara Ashadha Nakshatra - https://www.astrosaxena.com/uanaksh.
Sagittarius - As Uttara Ashadha is part of Sagittarius sign, Sagittarius and things represented by Sagittarius are important here. Sagittarius is the 9th sign of Zodiac Belt, hence it represents many things related with the 9th house of horoscope like Religion, Knowledge, Wisdom, Higher Learnings, Gurus, Teachings from your Father etc. Besides it also represents Coaching, Universities, Professors and Preachers, Higher Wisdom, Written Law of the Land etc. Sagittarius has 2 and half nakshatra which are Mula, Purva-Ashadha and Uttara-Ashadha. Sagittarius' lord is Jupiter.
Capricorn - As Uttara Ashadha is also part of Capricorn sign, Capricorn and things represented by Capricorn are also important here. Capricorn is the 10th sign of zodiac belt, hence it represents many things related with 10th house of horoscope like Law and Order, Government, Authority, Organisation, Discipline etc. Besides it also represents World outside your home and people, Fear and Anxiety etc. Capricorn is consisted of next 2 and half Nakshatra, i.e. Uttar-Ashadha, Shravana and Dhanishtha. Capricorn is ruled by Saturn and that's why it represents Fear and Anxiety.
Sun - As Sun rules Uttara Ashadha, Sun's position and dignity is important to know about the overall functioning of any planet in Uttara Ashadha.
Jupiter - As Jupiter rules Sagittarius, their position and dignity is important to know about the overall functioning of any planet in Uttara Ashadha/Sagittarius.
Saturn - As Saturn rules Capricorn, their position and dignity is important to know about the overall functioning of any planet in Uttara Ashadha/Capricorn
Houses Involved – Also, we can’t afford to forget the houses involved as a planet can be ruling different houses and sitting in different house for every person as per ascendant and planet’s position. To know overall affect, we have to consider the houses involved as those areas of life are being impacted.
Interpretation of Sun in Uttara Ashadha Nakshatra – Now, Sun is in own nakshatra, hence it can be termed as strong especially when it is in Sagittarius portion as its lord Jupiter is also friendly to Sun. Now, again after research of Mula and higher education of Purva Ashadha, it is time for reaping the results when Sun is in Capricorn. What will we do after getting higher education? We will try to apply same in our Career. So, this nakshatra and especially Sun sitting in it can make someone very career-driven person. Due to symbolism of Elephant Tusk, they can be very ambitious of high authoritative positions. In Sagittarius portion, they can be inclined towards such positions in field of academics or knowledge but in Capricorn portion, they can be inclined towards high positions in Govt or Law. Law remains a common interest as Sagittarius is also sign of Law. Due to impact of mythological story, the medical/surgery career is also their inclination. Whichever is field, one thing is sure that they will get success after much delay, hard work and perseverance especially if Sun is in Saturn's sign Capricorn. So overall, this is nakshatra of reaping results after hard work and most ambitious people can be seen from this position.
Role of Sun – As we are interpreting Sun only, we need not to separately see Sun's position as lord of Uttara Ashadha.
Role of Jupiter - Also, Jupiter placement is important to guide Sun in right direction, being Sagittarius lord.
Role of Saturn - Also, Saturn placement is important to guide Sun in right direction, being Capricorn lord.
Other Factors – And of course, we need to consider conjunction, aspects, house lordship, house position and dashas etc to know the exact results of Sun in Uttara Ashadha. So, we always need to take a holistic view of chart rather than just 1 planetary position.
Conclusion – So, this is how I see Sun in Uttara Ashadha can work in a chart.
Hope this helps. Please post any comment or query you may have.