Dusters for royal silver (small) (4)
I believe the answer is:
rags
'dusters' is the definition.
(I've seen this in another clue)
'royal silver small' is the wordplay.
'royal' becomes 'r' (common abbreviation e.g. RM - Royal Marine).
'silver' becomes 'Ag' (Ag is the chemical symbol for silver).
'small' becomes 's' (abbreviation - e.g. clothes size).
'r'+'ag'+'s'='RAGS'
'for' is the link.
(Other definitions for rags that I've seen before include "Small pieces of cloth (but can be glad)" , "tabloids" , "Small bits of waste cloth" , "Pieces of old cloth" , "Tattered clothes" .)