Conduct a sermon about a weapon (5)
I believe the answer is:
taser
'a weapon' is the definition.
(taser is a type of weapon)
'conduct a sermon about' is the wordplay.
'about' says the answer is hidden in the clue (the clue goes around or about the answer).
'TASER' is hidden in the letters of 'conduct a sermon'.
(Other definitions for taser that I've seen before include "Weapon firing electrified darts; stare (anag.)" , "police weapon introduced" , "Stun gun" , "Shocking device used by the police?" , "Electroshock weapon" .)