Bargain, much-liked — small piece (7)
I believe the answer is:
snippet
'small piece' is the definition.
(I've seen this before)
'bargain much-liked' is the wordplay.
'bargain' becomes 'snip' (slang term for a good deal).
'much-liked' becomes 'pet' (as in a pet project).
'snip'+'pet'='SNIPPET'
(Other definitions for snippet that I've seen before include "A small piece cut off" , "Small scrap" , "Newspaper extract" , "Fair --, knitwear style" , "Brief extract" .)