One inhibited by noisy petitioner (8)
I believe the answer is:
claimant
'petitioner' is the definition.
(thesaurus)
'one inhibited by noisy' is the wordplay.
'one' becomes 'i' (Roman numeral).
'inhibited by' is an insertion indicator (I've seen this in other clues).
'noisy' becomes 'clamant' ('clamant' can be similar in meaning to 'noisy').
'i' going within 'clamant' is 'CLAIMANT'.
(Other definitions for claimant that I've seen before include "Person taking legal action" , "Person seeking payout" , "Person demanding something as a right" , "One asking for something as a right" , "12-er" .)