Much appreciated series? It's something stunning (5)
I believe the answer is:
taser
'something stunning' is the definition.
(a taser shocks or stuns people)
'much appreciated series?' is the wordplay.
'much appreciated' becomes 'ta' (both are ways of saying thank you).
'series?' becomes 'ser' (abbreviation for series).
'ta'+'ser'='TASER'
'it's' is the link.
(Other definitions for taser that I've seen before include "Shocking device used by the police?" , "A shocking thing" , "Electroshock weapon" , "Shocking weapon" , "Stunning weapon" .)