One makes a noise disappearing -- one unseen (4)
I believe the answer is:
gong
'one makes a noise' is the definition.
(type of instrument)
'disappearing one unseen' is the wordplay.
'disappearing' becomes 'going' (going is a kind of disappearing).
'one' becomes 'i' (Roman numeral).
'unseen' suggests deleting specific letters.
'going' with 'i' taken away is 'GONG'.
(Other definitions for gong that I've seen before include "Dinner bell or slang medal" , "Dinner bell or slangy medal" , "Wordsworth's Boy; Dostoevsky's hero" , "Resonant metal disc" , "Instrument - award" .)