Ships that are fast? (5)
I believe the answer is:
fleet
This clue is a double definition.
'ships' is the first definition.
(eg a naval fleet)
'are fast?' is the second definition.
(similar in meaning)
'that' is the link.
(Other definitions for fleet that I've seen before include "Collection of company cars" , "Fast kind of armada?" , "Ships - quick!" , "vehicles owned by a company" , "Swift; armada" .)