Frustrated Christian’s superior and unruly fellow (8)
I believe the answer is:
blighted
'frustrated' is the definition.
(thesaurus)
'christian's superior and unruly fellow' is the wordplay.
'christian's superior' becomes 'Bligh' (superior of Fletcher Christian on HMS Bounty).
'and' is a charade indicator (letters next to each other).
'unruly fellow' becomes 'ted' (as in the Teddy Boy subculture).
'bligh'+'ted'='BLIGHTED'
(Other definitions for blighted that I've seen before include "Spoilt, harmed" , "Spoiled, harmed; infected" , "Withered with disease like potatoes in famine" , "Damaged" .)