Claret's changed colour (7)
I believe the answer is:
'colour' is the definition.
(I know that scarlet is a colour)
'claret's changed' is the wordplay.
'changed' indicates an anagram.
'clarets' with letters rearranged gives 'SCARLET'.
(Other definitions for scarlet that I've seen before include "Crimson" , "immoral" , "Shade of red" , "Murderer" , "Bright red of clarets" .)