Mock independent friend going without sex (7)
I believe the answer is:
imitate
'mock' is the definition.
(I've seen this before)
'independent friend going without sex' is the wordplay.
'independent' becomes 'i'.
'friend' becomes 'mate' (mate is a kind of friend).
'going without' means one lot of letters goes inside another ('without' can mean 'outside').
'sex' becomes 'it' (common euphemism).
'mate' enclosing 'it' is 'mitate'.
'i'+'mitate'='IMITATE'
(Other definitions for imitate that I've seen before include "I tame it (anag)" , "Copy or mimic" , "Copy, simulate" , "Copy (mannerisms)" , "Appear like, in behaviour or appearance" .)