Sample is lacking the second time? That's a shocker (5)
I believe the answer is:
taser
'shocker' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
(Other definitions for taser that I've seen before include "Police stun weapon" , "shocker" , "Stun gun" , "Weapon used to deliver a temporarily paralysing electric shock" , "A shocking thing" .)