Current partner admitting sex is fake (7)
I believe the answer is:
imitate
'is fake' is the definition.
(I've seen this before)
'current partner admitting sex' is the wordplay.
'current' becomes 'I' (symbol for electric current).
'partner' becomes 'mate' (synonyms).
'admitting' means one lot of letters goes inside another (admit can mean to welcome in or accept).
'sex' becomes 'it' (a common euphemism).
'mate' going around 'it' is 'mitate'.
'i'+'mitate'='IMITATE'
(Other definitions for imitate that I've seen before include "Appear like, in behaviour or appearance" , "Reproduce" , "I tame it (anag)" , "Follow suit" , "Copy or mimic" .)