Spirit label beginning to yellow (6)
I believe the answer is:
brandy
'spirit' is the definition.
(I've seen this before)
'label beginning to yellow' is the wordplay.
'label' becomes 'brand' (branding is a kind of labelling).
'beginning to' says to take the initial letters.
The initial letter of 'yellow' is 'y'.
'brand'+'y'='BRANDY'
(Other definitions for brandy that I've seen before include "Strong drink distilled from wine" , "Cognac, perhaps" , "See 20" , "warmer?" , "Distilled wine or fermented fruit juice" .)