Engineer a reign so corrupt (8)
I believe the answer is:
organise
'engineer' is the definition.
('engineer'->'organize' is in my internal thesaurus and 'ize'->'ise')
'a reign so corrupt' is the wordplay.
'corrupt' indicates anagramming the letters.
'a'+'reign'+'so'='areignso'
'areignso' anagrammed gives 'ORGANISE'.
(Other definitions for organise that I've seen before include "Plan, direct, co-ordinate" , "Arrange - as region (anag)" , "Catalogue" , "run" , "Set up, co-ordinate" .)