Slough put gold into service (6)
I believe the answer is:
morass
'slough' is the definition.
(I've seen this in another clue)
'gold into service' is the wordplay.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'into' means one lot of letters goes inside another.
'service' becomes 'mass' (mass is a church service).
'or' going into 'mass' is 'MORASS'.
'put' is the link.
(Other definitions for morass that I've seen before include "Bog - situation hard to get out of" , "Tract of swampy land" , "Muddled situation" , "Bog or marsh" , "Bog or swamp" .)