End of unusual treat - mine (9)
I believe the answer is:
terminate
'end' is the definition.
(I know that end can be written as terminate)
'unusual treat mine' is the wordplay.
'unusual' indicates anagramming the letters.
'treat'+'mine'='treatmine'
'treatmine' is an anagram of 'TERMINATE'.
'of' is the link.
(Other definitions for terminate that I've seen before include "Close" , "Stop" , "Cut short" , "Conclude" , "Put an end to, discontinue" .)