Hard-to-describe feeling (4)
I believe the answer is:
vibe
'hard-to-describe feeling' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for vibe that I've seen before include "Aura experienced instinctively" , "Aura given off by person/place" , "Perceptible aura" , "Atmosphere, feeling" , "Atmosphere, aura" .)