Eye trouble in misty environment (4)
I believe the answer is:
stye
'eye trouble' is the definition.
(I've seen this in another clue)
'in misty environment' is the wordplay.
'in' indicates a hidden word.
'STYE' is hidden in the letters of 'misty environment'.
(Other definitions for stye that I've seen before include "Inflammation on eyelid" , "Eye blemish" , "Climb" , "makes viewer sore" , "Inflammation around the eye" .)