Ships millions hoarded by a school for actors (6)
I believe the answer is:
armada
'ships' is the definition.
(I've seen this before)
'millions hoarded by a school for actors' is the wordplay.
'millions' becomes 'm' (abbreviation).
'hoarded by' means one lot of letters goes inside another (hoard can mean to hold onto).
'school for actors' becomes 'rada' (Royal Academy of Dramatic Art).
'a'+'rada'='arada'
'm' going inside 'arada' is 'ARMADA'.
(Other definitions for armada that I've seen before include "A great fleet of warships" , "sea-borne unit" , "lot of craft" , "Fleet Drake defeated" , "Large Spanish fleet" .)