Fight with police and a large old copper, perhaps (5,5)
I believe the answer is:
scrap metal
'old copper perhaps' is the definition.
(scrap metal might be copper)
'fight with police and a large' is the wordplay.
'fight' becomes 'scrap' (a scrap is a minor fight).
'with' means one lot of letters go next to another.
'police' becomes 'met' (London Metropolitan Police).
'and' means one lot of letters go next to another.
'large' becomes 'L' (eg in clothes sizes).
'scrap'+'met'+'a'+'l'='SCRAP-METAL'
(Other definitions for scrap metal that I've seen before include "reclaimed material" , "it's unwanted by industry?" , "Waste material for remelting" , "Get rid of gold, for instance" , ""Old iron"" .)