Second abstainer with a glower spotted (7)
I believe the answer is:
mottled
'spotted' is the definition.
(mottling is a kind of spotting)
'second abstainer with a glower' is the wordplay.
'second' becomes 'mo' (both are short periods of time).
'abstainer' becomes 'TT' (short for teetotaller, someone who avoids alcohol).
'with' means one lot of letters go next to another.
'a glower' becomes 'led' (I've seen this in other clues).
'mo'+'tt'+'led'='MOTTLED'
(Other definitions for mottled that I've seen before include "Blotchy" , "Blotched" , "Having blotches of colour" , "Marked with irregular patches of colour" , "with variable effect" .)