Rock star in hot spot (7)
I believe the answer is:
tarnish
'spot' is the definition.
(tarnishing is a kind of spotting)
'rock star in hot' is the wordplay.
'rock' is an anagram indicator (the solver must 'rock' the letters around).
'hot' becomes 'h'.
'star'+'in'='starin'
'starin' is an anagram of 'tarnis'.
'tarnis'+'h'='TARNISH'
(Other definitions for tarnish that I've seen before include "Stain or discolour, say metal" , "Cause to lose lustre, silver or reputation" , "Taint" , "Stain, metal or reputation" , "Lose lustre; sully" .)