Enduring corruption of bad rule (7)
I believe the answer is:
durable
'enduring' is the definition.
(thesaurus)
'corruption of bad rule' is the wordplay.
'corruption of' indicates an anagram.
'bad'+'rule'='badrule'
'badrule' with letters rearranged gives 'DURABLE'.
(Other definitions for durable that I've seen before include "Firm" , "Long-lasting and hard-wearing" , "Made to last" , "Rugged; long-lasting" , "existing for a long time" .)