Ships seized by war-mad admiral? (6)
I believe the answer is:
armada
'ships' is the definition.
(group of ships)
'seized by war-mad admiral?' is the wordplay.
'seized by' indicates a hidden word (the answer has been seized by the clue).
'ARMADA' can be found hidden inside 'war mad admiral'.
(Other definitions for armada that I've seen before include "A great fleet, ships or planes" , "The Spanish force" , "A great fleet - Spain had one" , "Large number of ships (Spanish?)" , "Old Spanish fleet" .)