Best man caught by friend putting ring on (7)
I believe the answer is:
optimal
'best man' is the definition.
'optimal' can be an answer for 'best' (optimal means the best). I'm unsure of the 'man' bit.
'caught by friend putting ring on' is the wordplay.
'caught by' indicates putting letters inside (I've seen this in other clues).
'friend' becomes 'pal' (pal can mean a friend).
'putting' becomes 'tim' (I am not sure about this - if you are sure you should believe this answer much more).
'ring' becomes 'O' (letter resembling a ring).
'on' is a charade indicator (letters next to each other).
'pal' going around 'tim' is 'ptimal'.
'ptimal' after 'o' is 'OPTIMAL'.
Can you help me to learn more?
(Other definitions for optimal that I've seen before include "Most desirable" , "couldn't be better" , "Most favouring" , "Plot aim (anag) - most favourable" , "In the best condition" .)