Swift ships (5)
I believe the answer is:
fleet
This clue is a double definition.
'swift' is the first definition.
(I know that swift can be written as fleet)
'ships' is the second definition.
(eg a naval fleet)
(Other definitions for fleet that I've seen before include "Naval force or collection of buses" , "Number of vehicles" , "bowler famously intercepted one once" , "collection of aircraft" , "Swift of foot - old London jail" .)