Power tested with Zener cards (3)
I believe the answer is:
esp
'power tested with zener cards' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for esp that I've seen before include "Apparent power to perceive things that others can't, initially" , "Second sight (abbr)" , "Initially, clairvoyance or telepathy" , "Apparent power to perceive things that others can't, in short" , "Extrasensory perception (abbrev.)" .)