Gold found in river stream (7)
I believe the answer is:
torrent
'stream' is the definition.
(torrent is a kind of stream)
'gold found in river' is the wordplay.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'found in' means one lot of letters goes inside another.
'river' becomes 'trent' (I've seen this before**).
'or' placed inside 'trent' is 'TORRENT'.
(Other definitions for torrent that I've seen before include "Turbulent flow" , "Heavy rain" , "Turbulent, swift-flowing stream" , "Overwhelming outpouring" , "Rapid stream" .)