Pained look (7)
I believe the answer is:
grimace
'pained look' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for grimace that I've seen before include "Contortion of face expressing pain" , "Glower" , "Smirk" , "Pull a face" , "Facial contortion expressive of pain or disgust" .)