Beer in animal skin is fit to market (8)
I believe the answer is:
saleable
'fit to market' is the definition.
'beer in animal skin' is the wordplay.
'beer' becomes 'ale' (I've seen this before).
'in' is an insertion indicator.
'animal skin' becomes 'sable' (sable is a kind of animal skin**).
'ale' placed inside 'sable' is 'SALEABLE'.
'is' acts as a link.
(Other definitions for saleable that I've seen before include "appropriate for market" , "good to buy" , "Fit for marketing" .)