Sound travels quickly in boats (8)
I believe the answer is:
dinghies
'boats' is the definition.
(dinghy is a kind of boat)
'sound travels quickly' is the wordplay.
'sound' becomes 'ding' (I've seen this before).
'travels quickly' becomes 'hies'.
'ding'+'hies'='DINGHIES'
'in' is the link.
(Other definitions for dinghies that I've seen before include "Small rowing boats" , "On the surface, they go along" , "Small open boats" .)