Let’s look at important things here –
Sun - Sun represents Personality, King, Government, Father, Authority, Career, Top Positions, Ego, Self Esteem, Health, Education etc.
Magha - Magha is nakshatra of Kings, Authority and Authoritative Positions. It is also nakshatra of celebrities. For more information on Magha, please check this - https://www.astrosaxena.com/maghnaksh.
Leo - As Magha is a part of Leo, Leo sign and its representations become important. Leo is 5th sign of zodiac belt, hence it represents the things associated with 5th house of horoscope like Love, Creativity, Arts, Being on Stage etc. Besides that, Leo is basically the Lion. This is the sign of feeling like King or Queen. Also, it is a sign of independence, Confidence, Ego, Self Esteem etc. Leo is consisted of 2 and half Nakshatra namely Magha, Purva-Phalguni and Uttara-Phalguni. Leo's lord is Sun..
Sun - As Sun rules Leo, Sun's position and dignity is important to know about the overall functioning of any planet in Magha/Leo.
Ketu - As Magha is ruled by Ketu, Ketu's position and dignity will also have an important role in functioning and results of any planet in Magha.
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 Magha Nakshatra – This is where Sun wants to be. Here, Sun is in own sign and in a nakshatra which is all about power, authority and high-status. Magha represents all the things truly represented by Leo. This person can be highly ambitious. He won't be satisfied by mediocre success or an average living. This person would love to be in the position of power and authority. Something inside will always push him to get into King-like position. It is a good position for being in high government positions or being any authority. They can also become celebrities, if they are into creative fields like arts or sports. Now, there are few things they need to take care of. They should not become power hungry or one who abuses their power. They should not attach themselves with egoistic attitude. It is very difficult to keep your feet on ground when Sun/Leo/Magha come together but this is what they need to do. If they are spiritually inclined through overall chart then they can be in authoritative position in spiritual field too. Challenge here is to use authority and power in a positive way and become a true leader. A true leader inspires others and make others as leaders but a fake leader is an insecured person who is fearful of losing his authority and hence he doesn't let others grow. I always give example of Imran Khan as true leader during his playing days as he could create other leaders. He was not afraid of losing his position in side which enabled him to create new leaders within the team. So, that is where Sun in Magha and Sun in Leo will work best.
Role of Sun – As we are interpreting Sun only, we need not to separately see Sun's position as Leo's lord.
Role of Ketu - Likewise, Ketu's placement is important to guide Sun in right direction, being Magha's 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 Magha. 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 Magha can work in a chart.
Hope this helps. Please post any comment or query you may have.