Occasionally grabs stark inch of stomach (7)
I believe the answer is:
gastric
'of stomach' is the definition.
(relating to the stomach)
'occasionally grabs stark inch' is the wordplay.
'occasionally' means one should take alternating letters (letters taken at regular intervals or occasions).
'grabs'+'stark'+'inch'='grabsstarkinch'
The alternating letters of 'grabsstarkinch' are 'GASTRIC'.
(Other definitions for gastric that I've seen before include "Pertaining to the stomach" , "Abdominal" , "Stomachic" , "affecting stomach" , "Intestinal" .)