Dream about having a weapon (5)
I believe the answer is:
armed
'having a weapon' is the definition.
'dream about' is the wordplay.
'about' indicates an anagram.
'dream' is an anagram of 'ARMED'.
(Other definitions for armed that I've seen before include "Supplied with weapons" , "equipped for fighting" , "with Browning?" , "Equipped with weapons" , "Prepared for attack" .)