Pick up from the armourer's (4)
I believe the answer is:
hear
'pick up' is the definition.
(hearing is a kind of picking up)
'from the armourer's' is the wordplay.
'from' indicates the answer is hidden within the clue.
'HEAR' can be found hidden inside 'the armourer'.
(Other definitions for hear that I've seen before include "Find out" , "Be informed of" , "Try (in court)" , "Hark" , "Get wind of" .)