Vulcan nonchalantly carries weapon (6)
I believe the answer is:
'weapon' is the definition.
(cannon is a kind of weapon)
'vulcan nonchalantly carries' is the wordplay.
'carries' says the answer is hidden in the clue.
'CANNON' is hidden in the letters of 'vulcan nonchalantly'.
(Other definitions for cannon that I've seen before include "shot playing billiards", "Gun sounds like a churchman", "The large gun sounds like a church dignitary", "Heavy artillery piece", "Howitzer".)