Remove top of instrument to find another one (4)
I believe the answer is:
lute
'find another one' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'remove top of instrument' is the wordplay.
'remove top of' means to remove the first letter (I've seen 'removes top' mean this).
'instrument' becomes 'flute' (flute is a kind of instrument).
'flute' with its initial letter taken away is 'LUTE'.
'to' is the link.
(Other definitions for lute that I've seen before include "Old plucked instrument" , "Ancient stringed instrument" , "Old stringed instrument with a pear-shaped body" , "instrument that minstrel played" , "Old musical instrument" .)