Suit: fine one, choice clothes (5)
I believe the answer is:
befit
'suit' is the definition.
(I know that suit can be written as befit)
'fine one choice clothes' is the wordplay.
'fine' becomes 'f' (abbreviation).
'one choice' becomes 'beit' (I can't explain this - if you can you should give a lot more credence to this answer).
'clothes' means one lot of letters goes inside another (some letters clothe or cover others).
'f' put within 'beit' is 'BEFIT'.
Can you help me to learn more?
(Other definitions for befit that I've seen before include "Be right and suitable for" , "Be appropriate for" , "Become, suit" .)