Finish at a pinch (5,3)
I believe the answer is:
knock off
I believe this is a double definition.
'finish' is the first definition.
(thesaurus)
'a pinch' is the second definition.
(thesaurus)
'at' is the link.
(Other definitions for knock off that I've seen before include "Stop work (informal)" , "finish work" , "steal or > kill" , "Do quickly" , "Stop work - steal" .)