Slough produces gold in bulk (6)
I believe the answer is:
morass
'slough' is the definition.
(I've seen this in another clue)
'gold in bulk' is the wordplay.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'in' indicates putting letters inside.
'bulk' becomes 'mass' (synonyms).
'or' put into 'mass' is 'MORASS'.
'produces' is the link.
(Other definitions for morass that I've seen before include "dangerous situation" , "Tract of soft, wet ground" , "Confusion" , "Bog - situation hard to get out of" , "Tract of swampy land" .)