Pain of hypochondriac heightened (4)
I believe the answer is:
ache
'pain' is the definition.
(ache is a kind of pain)
'of hypochondriac heightened' is the wordplay.
'of' says the answer is hidden in the clue.
'ACHE' is hidden in the letters of 'hypochondriac heightened'.
(Other definitions for ache that I've seen before include "painful" , "Long ? pain" , "Feel pain" , "Hanker" , "agony" .)