Reject short needle (4)
I believe the answer is:
spur
'needle' is the definition.
(thesaurus)
'reject short' is the wordplay.
'reject' becomes 'spurn' (synonyms).
'short' means to remove the last letter.
'spurn' with its final letter taken off is 'SPUR'.
(Other definitions for spur that I've seen before include "Goad; stimulus" , "Egg on or goad as horseman might" , "Incite to action" , "Rider's heel wheel" , "Spike on a horse-rider's boot" .)