Hassled, he'd admitted a right fool (8)
I believe the answer is:
harassed
'hassled' is the definition.
('harass' can be a synonym of 'hassle')
'he'd admitted a right fool' is the wordplay.
'admitted' is an insertion indicator.
'a right' becomes 'ar' (I've seen this in other clues).
'fool' becomes 'ass' (both can mean a stupid person).
'ar'+'ass'='arass'
'hed' placed around 'arass' is 'HARASSED'.
(Other definitions for harassed that I've seen before include "Constantly tormented" , "Pestered; under strain" , "in a state of torment" , "Annoyed and troubled continually" , "Badgered" .)