One magnet's orientation to hold copper for anvil (5)
I believe the answer is:
incus
'anvil' is the definition.
(Latin name for the anvil in the ear)
'one magnet's orientation to hold copper' is the wordplay.
'one' becomes 'i' (Roman numeral).
'magnet's orientation' becomes 'NS' (north and south poles).
'to hold' indicates putting letters inside.
'copper' becomes 'Cu' (chemical symbol).
'ns' placed around 'cu' is 'ncus'.
'i'+'ncus'='INCUS'
'for' acts as a link.
(Other definitions for incus that I've seen before include "Ear anvil bone" , "anvil (so we hear)" , "Middle-ear bone" , "part of sound system" , "Bone in the middle ear" .)