Claim to be confused regarding chemical processes in the body (9)
I believe the answer is:
metabolic
'regarding chemical processes in the body' is the definition.
'claim to be confused' is the wordplay.
'confused' indicates an anagram.
'claim'+'to'+'be'='claimtobe'
'claimtobe' anagrammed gives 'METABOLIC'.
(Other definitions for metabolic that I've seen before include "concerning reactions in body" , "Pertaining to chemical processes of life" , "affecting body processes" .)