Pole virtually redundant (4)
I believe the answer is:
spar
'pole' is the definition.
(spar is a kind of pole)
'virtually redundant' is the wordplay.
'virtually' means to remove the last letter (all but the last letter).
'redundant' becomes 'spare' ('spare' can be a synonym of 'redundant').
'spare' with its final letter removed is 'SPAR'.
(Other definitions for spar that I've seen before include "Raps with large beam" , "Raps with strong pole" , "Box - mineral - rod" , "Stout pole to support rigging" , "Raps with wooden beam" .)