Tiny bone is inlaid with new copper (5)
I believe the answer is:
incus
'tiny bone' is the definition.
'incus' can be an answer for 'bone' (I've seen this before). I'm unsure of the 'tiny' bit.
'is inlaid with new copper' is the wordplay.
'inlaid with' indicates putting letters inside.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'copper' becomes 'cu' (chemical symbol).
'n'+'cu'='ncu'
'is' going around 'ncu' is 'INCUS'.
Can you help me to learn more?
(Other definitions for incus that I've seen before include "Bone in the middle ear" , "Middle-ear bone" , "Ear anvil bone" , "Hard part of the Listener" , "anvil (so we hear)" .)