Disdainfully ignore small growth on foot (5)
I believe the answer is:
scorn
'disdainfully ignore' is the definition.
(I know that to scorn is to contemptuously cut)
'small growth on foot' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'growth on foot' becomes 'corn' (corn can thickened skin on a foot).
's'+'corn'='SCORN'
(Other definitions for scorn that I've seen before include "Reject contemptuously" , "Disgust" , "Open disrespect" , "Hold in contempt" , "Open contempt, disdain" .)