Get key to engrave (5)
I believe the answer is:
fetch
'get' is the definition.
(synonyms)
'key to engrave' is the wordplay.
'key' becomes 'f' (musical key).
'to engrave' becomes 'etch' (I've seen this before).
'f'+'etch'='FETCH'
(Other definitions for fetch that I've seen before include "Collect" , "Order to dog to retrieve thrown stick" , "Sell for" , "Go and bring back" , "Achieve (price) when sold" .)