Pole not entirely free (4)
I believe the answer is:
spar
'pole' is the definition.
(I know that spar is a type of pole)
'not entirely free' is the wordplay.
'not entirely' means to remove the last letter (most but not all of the word).
'free' becomes 'spare' (synonyms).
'spare' with its last letter removed is 'SPAR'.
(Other definitions for spar that I've seen before include "possibly rigged" , "Box (lightly) - fight (verbally)" , "Pole to support sails, rigging etc" , "Pole used in boat etc - box" , "Yard" .)