End with Romeo in fit of temper (5)
I believe the answer is:
strop
'fit of temper' is the definition.
'end with romeo in' is the wordplay.
'end' becomes 'stop' ('stop' can be a synonym of 'end').
'with' is an insertion indicator.
'romeo in' becomes 'r' (I can't explain this - if you can you should give a lot more credence to this answer).
'stop' placed around 'r' is 'STROP'.
(Other definitions for strop that I've seen before include "Sharpen on piece of leather" , "Prime cutthroat" , "rage" , "Paddy" , "wobbly" .)