Wear a long face (4)
I believe the answer is:
mope
'wear a long face' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for mope that I've seen before include "Move around slowly and aimlessly" , "Feel dejected and apathetic" , "Move listlessly and aimlessly" , "Be listless over poem" , "Pine - sulk" .)