Notice a pimple (4)
I believe the answer is:
spot
I believe this is a double definition.
'notice' is the first definition.
(thesaurus)
'a pimple' is the second definition.
(thesaurus)
(Other definitions for spot that I've seen before include "jam > stain" , "place on TV programme" , "Mark, dot" , "Notice; skin blemish" , "Identify" .)