Unpopular spots (4)
I believe the answer is:
acne
'unpopular spots' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for acne that I've seen before include "Spotty complaint" , "Teenage spots" , "Skin problem, mainly of teenagers" , "Spotty skin condition" , "Skin condition prevalent among teenagers" .)