"That's revolting!" (5)
I believe the answer is:
gross
'that's revolting' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for gross that I've seen before include "Twelve dozen" , "Repulsively large" , "Without deduction; flagrant" , "result of a 12 x 12 construction" , "A dozen dozen - repellently bulky" .)