Sensation that's revealed in backbiting letters (6)
I believe the answer is:
tingle
'sensation' is the definition.
(thesaurus)
'revealed in backbiting letters' is the wordplay.
'revealed in' says the answer is hidden in the clue.
'TINGLE' can be found hidden inside 'backbiting letters'.
'that's' acts as a link.
(Other definitions for tingle that I've seen before include "shocking sensation" , "Sensational thrill" , "Stinging or thrilling sensation" , "Throb" , "Prickling or slightly stinging sensation" .)