White gold plating pound pieces (7)
I believe the answer is:
albumen
'white' is the definition.
(thesaurus)
'gold plating pound pieces' is the wordplay.
'gold' becomes 'au' (Au is the chemical symbol for gold).
'plating' indicates putting letters inside (I've seen this in other clues).
'pound' becomes 'lb' ('lb' can be a synonym of 'pound').
'pieces' becomes 'men' ('man' can be a synonym of 'piece'**).
'au' placed around 'lb' is 'albu'.
'albu'+'men'='ALBUMEN'
(Other definitions for albumen that I've seen before include "White poacher" , "Egg's white" , "The white part of an egg" , "Egg-white" .)