Old metal cut at edges, obsolete (7)
I believe the answer is:
extinct
'obsolete' is the definition.
(I've seen this before)
'old metal cut at edges' is the wordplay.
'old' becomes 'ex' (prefix meaning former or onetime).
'metal' becomes 'tin' (tin is a kind of metal).
'at edges' suggests removing the centre (only letters at the edges).
'cut' with its middle removed is 'ct'.
'ex'+'tin'+'ct'='EXTINCT'
(Other definitions for extinct that I've seen before include "(Species) lost" , "Defunct" , "Long gone, like te dinosaur" , "Having died out, like the dinosaur" , "(Of a volcano) dead" .)