Muscles in with article for drink (8)
I believe the answer is:
absinthe
'drink' is the definition.
(absinthe is a kind of drink)
'muscles in with article' is the wordplay.
'muscles' becomes 'abs' (I've seen this before).
'with' is a charade indicator (letters next to each other).
'article' becomes 'the' (the 'definite article' part of speech).
'abs'+'in'+'the'='ABSINTHE'
'for' acts as a link.
(Other definitions for absinthe that I've seen before include "Aniseed-flavoured liqueur" , "Green wormwood drink" , "Liqueur - the basin (anag)" , "intoxicant" , "Bitter liqueur" .)