The face of a fool (3)
I believe the answer is:
mug
I believe this clue is a double definition.
'the face' is the first definition.
(informal term for face)
'a fool' is the second definition.
(I know that fool can be written as mug)
'of' is the link.
(Other definitions for mug that I've seen before include "Tankard" , "Vessel for a bit of a fool" , "Slangy victim, by gum" , "A person easily deceived, by gum" , "Drinking vessel for a chump" .)