Awkward writer upset during sex (5)
I believe the answer is:
inept
'awkward' is the definition.
(I know that awkward can be written as inept)
'writer upset during sex' is the wordplay.
'writer' becomes 'pen' (something which writes).
'upset' shows that the letters should be reversed in order.
'during' indicates putting letters inside.
'sex' becomes 'it' (common euphemism).
'pen' backwards is 'nep'.
'nep' put into 'it' is 'INEPT'.
(Other definitions for inept that I've seen before include "Awkward, clumsy" , "Maladroit" , "Unsuitable, clumsy" , "Clumsy and incompetent" , "Lousy" .)