We're told gag, an unfortunate sort (6)
I believe the answer is:
wretch
'an unfortunate sort' is the definition.
(an unfortunate person)
'we're told gag' is the wordplay.
'we're told' shows a homophone (sound like).
'gag' becomes 'retch' (I've seen this before).
'retch' is a homophone of 'WRETCH'.
(Other definitions for wretch that I've seen before include "Good-for-nothing" , "Swine" , "Contemptible person" , "Someone to be pitied" , "A pitiful, unfortunate person" .)