Final move is to examine partner (9)
I believe the answer is:
checkmate
'final move' is the definition.
'to examine partner' is the wordplay.
'to examine' becomes 'check' (checking is a kind of examining).
'partner' becomes 'mate' ('mate' can be a synonym of 'partner').
'check'+'mate'='CHECKMATE'
'is' is the link.
(Other definitions for checkmate that I've seen before include "Chess game ending" , "you lose!" , "Winning call on board" , "game's up now" , "Defeat totally" .)