Have contempt for small crop (5)
I believe the answer is:
scorn
'have contempt for' is the definition.
(to scorn is to reject or look down upon)
'small crop' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'crop' becomes 'corn' (I've seen this before).
's'+'corn'='SCORN'
(Other definitions for scorn that I've seen before include "Look at with disdain" , "Spurn" , "Contumely" , "Extreme contempt" , "Deride, show contempt for" .)