Part to go round audibly (4)
I believe the answer is:
role
'part' is the definition.
('role' can be a synonym of 'part')
'go round audibly' is the wordplay.
'go round' becomes 'roll' (I've seen this in other clues).
'audibly' shows a homophone (sound like).
'roll' is a homophone of 'ROLE'.
'to' is the link.
(Other definitions for role that I've seen before include "Part, portrayal" , "Function; part" , "Actor's part" , "Function in life" , "Part (in drama)" .)