Dressed for a military operation, we hear (7)
I believe the answer is:
arrayed
'dressed' is the definition.
(I've seen this in another clue)
'military operation we hear' is the wordplay.
'military' becomes 'ar' (I am not sure about this - if you are sure you should believe this answer much more).
'operation' becomes 'raid' (raid is a kind of operation).
'we hear' shows a homophone (sound like).
'raid' sounds like 'rayed'.
'ar'+'rayed'='ARRAYED'
'for a' is the link.
Can you help me to learn more?
(Other definitions for arrayed that I've seen before include "Ordered" , "Formed up" , "Decoratively assembled" , "Marshalled; (finely) dressed" , "Displayed in an arrangement" .)