Most junior solver finding gents busy (8)
I believe the answer is:
youngest
'most junior' is the definition.
('young' is associated in meaning with 'junior')
'solver finding gents busy' is the wordplay.
'solver' becomes 'you' (the person solving the clue!).
'finding' says to put letters next to each other.
'busy' indicates anagramming the letters.
'gents' with letters rearranged gives 'ngest'.
'you'+'ngest'='YOUNGEST'
(Other definitions for youngest that I've seen before include "Most immature" , "Last-born" , "Least elderly" , "last born" , "least experienced" .)