Forehead with new tan (5)
I believe the answer is:
brown
'tan' is the definition.
(I've seen this before)
'forehead with new' is the wordplay.
'forehead' becomes 'brow' ('brow' can be a synonym of 'forehead').
'with' is a charade indicator (letters next to each other).
'new' becomes 'n'.
'brow'+'n'='BROWN'
(Other definitions for brown that I've seen before include "Former PM" , "Rugby hero" , "Prime Minister, 2007-2010" , "Colour (at No 11?)" , "Kind of sweetener" .)