Frank lover describes bit of lovemaking (5)
I believe the answer is:
bluff
'frank' is the definition.
('bluff' can be a synonym of 'frank')
'lover describes bit of lovemaking' is the wordplay.
'lover' becomes 'buff' ('buff' can be a synonym of 'lover'**).
'describes' is an insertion indicator (describe can mean to form the outline of).
'bit of' says to take the initial letters.
The first letter of 'lovemaking' is 'l'.
'buff' enclosing 'l' is 'BLUFF'.
(Other definitions for bluff that I've seen before include "Challengers may call it" , "Feign" , "Pretend your position is stronger than it really is" , "Bank - subterfuge" , "Try to fool in poker game" .)