Fellow has to squeeze inside clerical garment (7)
I believe the answer is:
maniple
'clerical garment' is the definition.
(garment worn by clergymen)
'fellow has to squeeze' is the wordplay.
'fellow' becomes 'male' (fellow is a term for a man).
'has' means one lot of letters goes inside another.
'to squeeze' becomes 'nip' ('nip' can be a synonym of 'squeeze').
'male' placed around 'nip' is 'MANIPLE'.
'inside' is the link.
(Other definitions for maniple that I've seen before include "Some legionaries" , "vestment no longer used" , "Part of legion" , "company" , "Some old soldiers" .)