What a serial! Characters in it provide a shocker (5)
I believe the answer is:
taser
'a shocker' is the definition.
(something which gives electric shocks)
'what a serial characters in it' is the wordplay.
'in it' says the answer is hidden in the clue (I've seen this in other clues).
'TASER' can be found hidden inside 'what a serial characters'.
'provide' is the link.
(Other definitions for taser that I've seen before include "The weapon delivers a temporary paralysing electric shock" , "PC kit" , "Gun firing electrified barbs" , "Electrical weapon" , "Electroshock weapon" .)