Quietly change nappies with an instrument (8)
I believe the answer is:
panpipes
'an instrument' is the definition.
(I've seen this before)
'quietly change nappies' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'change' indicates anagramming the letters.
'nappies' anagrammed gives 'anpipes'.
'p'+'anpipes'='PANPIPES'
'with' is the link.
(Other definitions for panpipes that I've seen before include "Crude wind instrument" , "Musical wind instrument - syrinx" , "Folk instrument" , "Simple wind instrument" , "Musical instrument made of reeds of different lengths" .)