Good man fed to unpleasant chap a Mexican dish (7)
I believe the answer is:
tostada
'mexican dish' is the definition.
'good man fed to unpleasant chap a' is the wordplay.
'good man' becomes 'st'.
'fed to' indicates putting letters inside.
'unpleasant chap' becomes 'toad'.
'st' inserted into 'toad' is 'tostad'.
'tostad'+'a'='TOSTADA'
(Other definitions for tostada that I've seen before include "Mexican topped pancake" , "Mexican food" , "Crisp 15 down" , "spicy food" .)