This person's gripped by organ sound (5)
I believe the answer is:
noise
'sound' is the definition.
(noise is a kind of sound)
'this person's gripped by organ' is the wordplay.
'this person' becomes 'i'.
'gripped by' is an insertion indicator.
'organ' becomes 'nose' (nose is a kind of organ**).
'i' put into 'nose' is 'NOISE'.
(Other definitions for noise that I've seen before include "Unstructured sound" , "Unwanted sounds" , "Clamour" , "Hum" , "Loud or unpleasant sound" .)