Fortified wine’s knocked back, in a bad mood (5)
I believe the answer is:
strop
'a bad mood' is the definition.
(I've seen this before)
'fortified wine's knocked back' is the wordplay.
'fortified wine's' becomes 'port's' (port is a type of fortified wine).
'knocked back' shows that the letters should be reversed in order.
'ports' in reverse letter order is 'STROP'.
'in' is the link.
(Other definitions for strop that I've seen before include "wobbly" , "Bad temper - sharpen (a razor)" , "rage" , "Prime cutthroat" , "Display of temper" .)