Turning knocks into a pole (4)
I believe the answer is:
spar
'a pole' is the definition.
(I know that spar is a type of pole)
'turning knocks' is the wordplay.
'turning' shows that the letters should be reversed in order.
'knocks' becomes 'raps' ('rap' can be a synonym of 'knock').
'raps' back-to-front is 'SPAR'.
'into' is the link.
(Other definitions for spar that I've seen before include "possibly rigged" , "supporting member" , "Crystalline mineral" , "Stout pole to support rigging" , "Train at boxing; mineral" .)