A drama about ships (6)
I believe the answer is:
armada
'ships' is the definition.
(group of ships)
'a drama about' is the wordplay.
'about' indicates an anagram.
'drama' with letters rearranged gives 'rmada'.
'a'+'rmada'='ARMADA'
(Other definitions for armada that I've seen before include "Naval fighting force" , "1588 sea battle" , "Fleet of armed ships" , "vessels" , "force of the sea" .)