A fleet of warships (6)
I believe the answer is:
armada
'a fleet of warships' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for armada that I've seen before include "Spanish fleet sent in 1588 to escort an invasion of England" , "Fighting unit" , "Fleet of armed ships" , "Navy" , "1588 sea battle" .)