Almost disdain an incentive (4)
I believe the answer is:
spur
'an incentive' is the definition.
(thesaurus)
'almost disdain' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'disdain' becomes 'spurn' ('spurn' can be a synonym of 'disdain').
'spurn' with its final letter taken off is 'SPUR'.
(Other definitions for spur that I've seen before include "Rider's heel wheel" , "Cowboy's goading instrument" , "Goad - incentive" , "branch road" , "outcrop" .)