To end the fight for a cause in criminal! (7)
I believe the answer is:
treason
'cause in criminal' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'to end the fight' 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 found in the answer.
The remaining letters 'reason' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'for a' is the link.
Can you help me to learn more?
(Other definitions for treason that I've seen before include "Stare on (anag.)" , "Betrayal of one's nation" , "Criminal attempt to overthrow a government" , "rebellion" , "Lese-majesty" .)