Revolutionary again took weapon (5)
I believe the answer is:
taser
'weapon' is the definition.
(taser is a type of weapon)
'revolutionary again took' is the wordplay.
'revolutionary' says the letters should be written backwards (letters revolve around).
'again' becomes 're' (prefix meaning 'again').
'took' becomes 'sat' (sit can mean to take an exam).
're'+'sat'='resat'
'resat' in reverse letter order is 'TASER'.
(Other definitions for taser that I've seen before include "Stunning device" , "shocker" , "Stunning weapon" , "Device using electrified darts to stun" , "Electrical weapon" .)