Old bag from Turkey available for purchase (5)
I believe the answer is:
trout
'old bag' is the definition.
(I've seen this before)
'turkey available for purchase' is the wordplay.
'turkey' becomes 'tr' (abbreviation eg in internet addresses).
'available for purchase' becomes 'out' (eg a book that's been published is out).
'tr'+'out'='TROUT'
'from' acts as a link.
(Other definitions for trout that I've seen before include "Commonly caught fish" , "interfering old woman" , "Edible fish" , "air" , "Tutor (anag.)" .)