Imagine being armed, somehow (5)
I believe the answer is:
dream
'imagine' is the definition.
(dreaming is a kind of imagining)
'armed somehow' is the wordplay.
'somehow' is an anagram indicator.
'armed' is an anagram of 'DREAM'.
'being' is the link.
(Other definitions for dream that I've seen before include "Cherished desire" , "Cherished hope; reverie" , "Nocturnal vision" , "Aspiration" , "Something imaginary" .)