Bearing armour to post (7)
I believe the answer is:
airmail
'to post' is the definition.
(airmailing is a kind of posting)
'bearing armour' is the wordplay.
'bearing' becomes 'air' (both can mean an attitude or pose).
'armour' becomes 'mail' (mail is a kind of armour).
'air'+'mail'='AIRMAIL'
(Other definitions for airmail that I've seen before include "overseas post?" , "Flying service" , "Letters carried by plane" , "It's marked "par avion"" , "Flying post?" .)