Medium ability (3)
I believe the answer is:
esp
'medium ability' 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 "Initially, clairvoyance or telepathy" , "Apparent power to perceive things that others can't, initially" , "Extrasensory perception (abbrev.)" , "Second sight (abbr)" , "Apparent power to perceive things that others can't, in short" .)