Bad rule surprisingly long-lasting (7)
I believe the answer is:
durable
'long-lasting' is the definition.
(synonyms)
'bad rule surprisingly' is the wordplay.
'surprisingly' is an anagram indicator (a surprising ordering of the letters).
'bad'+'rule'='badrule'
'badrule' is an anagram of 'DURABLE'.
(Other definitions for durable that I've seen before include "Hardy" , "existing for a long time" , "Likely to last" , "Capable of lasting" , "Long-lasting and hard-wearing" .)