A French male in Piccadilly ends weak (4)
I believe the answer is:
puny
'weak' is the definition.
(similar in meaning)
'a french male in piccadilly ends' is the wordplay.
'a french male' becomes 'un' ('a' translated into French with masculine nouns).
'in' indicates putting letters inside.
'ends' suggests removing the centre.
'piccadilly' with its centre taken out is 'py'.
'un' placed within 'py' is 'PUNY'.
(Other definitions for puny that I've seen before include "in need of development" , "Slight" , "Feeble, under-sized" , "Small and weak" , "Weak - unimportant" .)