Clumsy writer getting upset during sex (5)
I believe the answer is:
inept
'clumsy' is the definition.
(synonyms)
'writer getting upset during sex' is the wordplay.
'writer' becomes 'pen' (I've seen this before).
'getting upset' shows that the letters should be reversed in order.
'during' means one lot of letters goes inside another.
'sex' becomes 'it' (a common euphemism).
'pen' reversed gives 'nep'.
'nep' placed into 'it' is 'INEPT'.
(Other definitions for inept that I've seen before include "lacks skill" , "Clumsy, bungling" , "Unskilful or unsuitable" , "Showing a lack of competence" , "Clumsy, out of place" .)