Blade for beheading a pig (3)
I believe the answer is:
oar
'blade' is the definition.
(blade is the word for oar in competitive rowing)
'beheading a pig' is the wordplay.
'beheading' means to remove the first letter.
'a pig' becomes 'boar' (I've seen this before).
'boar' with its initial letter taken off is 'OAR'.
'for' acts as a link.
(Other definitions for oar that I've seen before include "I'm involved in row" , "propellor" , "Propelling blade" , "Pusher" , "Propelling pole" .)