Tension afflicts US 'pens' -- edgy jails (8)
I believe the answer is:
suspense
'tension' is the definition.
(suspense can mean tension or uncertainty)
'afflicts us pens edgy jails' is the wordplay.
'jails' says the answer is hidden in the clue (the answer is jailed within the clue).
'SUSPENSE' can be found hidden inside 'afflicts us pens edgy'.
(Other definitions for suspense that I've seen before include "State of anxiety while waiting" , "State of nervous uncertainly" , "State of nervous or excited tension or uncertainty" , "Nervous uncertainty; cessation" , "feature of exciting fiction?" .)