Notice; pimple (4)
I believe the answer is:
spot
This clue is a double definition.
'notice' is the first definition.
(spot can mean to notice or observe)
'pimple' is the second definition.
(I've seen this before)
(Other definitions for spot that I've seen before include "jam > stain" , "Discern - mark" , "Observe - locality" , "20 [MARK]" , "Predicament" .)