Refuse to give incentive to knight (5)
I believe the answer is:
spurn
'refuse' is the definition.
(spurning is a kind of refusing)
'give incentive to knight' is the wordplay.
'give' says to put letters next to each other.
'incentive' becomes 'spur' (I've seen this before).
'to knight' becomes 'n' (chess).
'spur' put next to 'n' is 'SPURN'.
'to' is the link.
(Other definitions for spurn that I've seen before include "Refuse with contempt" , "Show contempt for" , "Reject scornfully, say unwanted suitor" , "Humber lighthouse" , "Treat with contempt" .)