Military aircraft (6)
'military aircraft' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for bomber that I've seen before include "warplane" , "It may be smoked" , "Eg, Lancaster, Vulcan" , "military plane" , "Zip-up garment elasticated at the waist and cuffs" .)
(Other definitions for dive bomber that I've seen before include "gannet?" , "military craft" , "Jolly threatening" .)