Fly in the ointment when top removed for the allergic reaction (4)
I believe the answer is:
itch
'allergic reaction' is the definition.
(I've seen this in another clue)
'fly in the ointment when top removed' is the wordplay.
I cannot really understand how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
The remaining letters 'ich' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'for the' acts as a link.
Can you help me to learn more?
(Other definitions for itch that I've seen before include "Irritating pain" , "Rash reaction?" , "Long" , "Burning" , "It needs to be scratched" .)