Facial expression of displeasure (5)
I believe the answer is:
frown
'facial expression of displeasure' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for frown that I've seen before include "Wrinkling of forehead" , "Wrinkle one's forehead in disapproval, anger etc" , "Sullen look" , "Look displeased" , "Dirty look" .)