Sells disheartened rescue dogs (7)
I believe the answer is:
retails
'sells' is the definition.
(retailing is a kind of selling)
'disheartened rescue dogs' is the wordplay.
'disheartened' says to hollow out the word (remove centre letters) (the middle or heart is removed).
'dogs' becomes 'tails' (dog and tail can both mean to follow).
'rescue' with its centre taken out is 're'.
're'+'tails'='RETAILS'
(Other definitions for retails that I've seen before include "Sells" , "Peddles" .)