New plates may be made of metal (6)
I believe the answer is:
staple
'be made of metal' is the definition.
The answer and definition can be both substances as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'new plates' is the wordplay.
'new' indicates anagramming the letters.
'plates' anagrammed gives 'STAPLE'.
'may' is the link.
Can you help me to learn more?
(Other definitions for staple that I've seen before include "Main element" , "e.g. rice, sweetcorn ..." , "Main, important" , "Principle - fixer" , "Secure" .)