Bed made up in exotic skin is available to buy immediately (2,5)
I believe the answer is:
in stock
'available to buy immediately' is the definition.
(as in a product already in stock)
'bed made up in exotic skin' is the wordplay.
'bed' becomes 'cot' (cot is a kind of bed).
'made up' says the letters should be written backwards (in a down clue, letters go up).
'in' is an insertion indicator.
'exotic' is an anagram indicator (an unusual form of the letters).
'cot' reversed gives 'toc'.
'skin' with letters rearranged gives 'insk'.
'toc' put within 'insk' is 'IN STOCK'.
'is' is the link.
(Other definitions for in stock that I've seen before include "On the shelf" , "available" , "Held by a shop" , "Where one may have cooked any meat" .)