Unpleasant, repugnant (5)
I believe the answer is:
nasty
This clue is a double definition.
'unpleasant' is the first definition.
(nasty can mean unpleasant or horrible)
'repugnant' is the second definition.
(I've seen this before)
(Other definitions for nasty that I've seen before include "Horrid, repugnant" , "Mean" , "Awful" , "Foul" , "rank" .)