As simpleton, face attack (3)
I believe the answer is:
mug
'attack' is the definition.
(thesaurus)
I can't explain the remainder of the clue.
(Other definitions for mug that I've seen before include "Large drinking vessel or slang victim" , "Drinking vessel; rob" , "Drinking vessel for a chump" , "Sucker - drinking vessel" , "Gullible person" .)