Copy something that’s still around, article filled with power (7)
I believe the answer is:
replica
'copy' is the definition.
(I know that replica is a type of copy)
'something that's still around article filled with power' is the wordplay.
'something that's still around' becomes 'relic' (something remaining from an earlier period).
'article' becomes 'a' (the indefinite article in English).
'filled with' means one lot of letters goes inside another.
'power' becomes 'p' (symbol in physics).
'relic'+'a'='relica'
'relica' enclosing 'p' is 'REPLICA'.
(Other definitions for replica that I've seen before include "Exact copy or model" , "Reproduction, exact copy" , "Parcel I arranged as exact copy" , "Copy original" , "Reproduction, fascsimile" .)