Defeated, have to amputate (3,3)
I believe the answer is:
saw off
This clue is a double definition.
'defeated' is the first definition.
(to see off can mean to defeat)
'to amputate' is the second definition.
'have' is the link.
(Other definitions for saw off that I've seen before include "lop" , "escorted to departure" , "Forced to leave" .)