Bomber following one in the role of peace protester (6)
I believe the answer is:
fiasco
'bomber' is the definition.
(something which bombs or is a disaster)
'following one in the role of peace protester' is the wordplay.
'following' becomes 'f.' (used when citing page numbers etc).
'one' becomes 'I' (Roman numeral).
'in the role of' becomes 'as' (as in an actor appearing as a character).
'peace protester' becomes 'co' (abbreviation for conscientious objector).
'f'+'i'+'as'+'co'='FIASCO'
(Other definitions for fiasco that I've seen before include "A ludicrous failure, a shambles" , "Total debacle" , "washout" , "Utter failure, debacle" , "Utter and ridiculous failure" .)