Star devouring liqueur? It's a slippery slope (3,3)
I believe the answer is:
ski run
'a slippery slope' is the definition.
(slope which people ski on)
'star devouring liqueur?' is the wordplay.
'star' becomes 'sun' (Sun is an example).
'devouring' is an insertion indicator.
'liqueur?' becomes 'kir' (type of wine).
'sun' placed around 'kir' is 'SKI RUN'.
'it's' acts as a link.
(Other definitions for ski run that I've seen before include "Winter sports slope" , "A trail for winter sportsmen" , "Recreational snow slope" , "Downhill course in winter" , "Boggy, swampy" .)