Lives dangerously after living once on river of molten metal (11)
I believe the answer is:
quicksilver
'molten metal' is the definition.
(historical name for mercury)
'lives dangerously after living once on river' is the wordplay.
'dangerously' is an anagram indicator (the letter order is damaged or endangered).
'after' means one lot of letters go next to another.
'living once' becomes 'quick' ('quick' could historically mean 'living').
'on river' becomes 'r' (I've seen this in other clues).
'lives' anagrammed gives 'silve'.
'silve' put after 'quick' is 'quicksilve'.
'quicksilve'+'r'='QUICKSILVER'
'of' is the link.
(Other definitions for quicksilver that I've seen before include "Liquid mercury" , "Element of dentistry" , "so rapid" , "Mercury - volatile" .)