On the beach remains source of metal (6)
I believe the answer is:
ashore
'on the beach' is the definition.
(I've seen this in another clue)
'remains source of metal' is the wordplay.
'remains' becomes 'ash' (remains of a fire).
'source of metal' becomes 'ore' (I've seen this before).
'ash'+'ore'='ASHORE'
(Other definitions for ashore that I've seen before include "Hoarse being no longer at sea" , "in port?" , "On(to) dry land" , "Going on land from sea" , "Aground" .)