Great success as one blocking corruption (4)
I believe the answer is:
riot
'great success' is the definition.
(thesaurus)
'one blocking corruption' is the wordplay.
'one' becomes 'i' (Roman numeral).
'blocking' means one lot of letters goes inside another.
'corruption' becomes 'rot' (I've seen this before).
'i' inserted into 'rot' is 'RIOT'.
'as' acts as a link.
(Other definitions for riot that I've seen before include "Wild revelry" , "The unruly may run this" , "A public affray or disturbance" , "Take to the streets" , "unrestrained revelry" .)