Soft, soft metal to make a case (5)
I believe the answer is:
plead
'make a case' is the definition.
(I've seen this in another clue)
'soft soft metal' is the wordplay.
'soft' becomes 'p' (musical abbreviation for piano, 'soft').
'soft metal' becomes 'lead' (I've seen this before).
'p'+'lead'='PLEAD'
'to' is the link.
(Other definitions for plead that I've seen before include "Argue (a position in court)" , "Argue (for a cause)" , "Request" , "Supplicate" , "Say one is guilty or not guilty" .)