River of gold - one with no cobalt! (7)
I believe the answer is:
orinoco
'river' is the definition.
(Orinoco River is an example)
'gold one with no cobalt' is the wordplay.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'one' becomes 'i' (Roman numeral).
'with' is a charade indicator (letters next to each other).
'cobalt' becomes 'co' (Co is the chemical symbol for cobalt).
'or'+'i'+'no'+'co'='ORINOCO'
'of' acts as a link.
(Other definitions for orinoco that I've seen before include "Womble; S. Amer. river" , "resident on Wimbledon Common" , "may be seen running through South America" , "South American river flowing into the Atlantic" , "South-American river" .)