Tour de force from principal oarsman (12)
I believe the answer is:
masterstroke
'tour de force' is the definition.
'principal oarsman' is the wordplay.
'principal' becomes 'master' (master is a kind of principal).
'oarsman' becomes 'stroke' (I've seen this before).
'master'+'stroke'='MASTERSTROKE'
'from' is the link.
(Other definitions for masterstroke that I've seen before include "outstanding piece of strategy" , "Brilliant act" , "Clever idea" .)