Claimant cares about involving copper (7)
I believe the answer is:
accuser
'claimant' is the definition.
(synonyms)
'cares about involving copper' is the wordplay.
'about' indicates an anagram.
'involving' indicates putting letters inside.
'copper' becomes 'cu' (chemical symbol).
'cares' anagrammed gives 'acser'.
'acser' enclosing 'cu' is 'ACCUSER'.
(Other definitions for accuser that I've seen before include "Person charging" , "he's pointing the finger" , "Person making a charge" , "person raising charges" , "Zola, for example" .)