Tan blazer - smart! (7)
I believe the answer is:
sunburn
'tan' is the definition.
(synonyms)
'blazer smart' is the wordplay.
'blazer' becomes 'sun' (I've seen this in other clues).
'smart' becomes 'burn' (burning is a kind of smarting).
'sun'+'burn'='SUNBURN'
(Other definitions for sunburn that I've seen before include "Tan (or unsuccessful attempt at it)" , "Overexposure to UV" , "Solar skin damage" , "Redness of the skin caused by solar rays" , "Effect of too much UV" .)