Lived wildly, the rascal! (5)
I believe the answer is:
devil
'the rascal' is the definition.
(thesaurus)
'lived wildly' is the wordplay.
'wildly' indicates anagramming the letters.
'lived' anagrammed gives 'DEVIL'.
(Other definitions for devil that I've seen before include "Lucifer" , "Imp" , "Terror" , "Demon" , "Beelzebub, Satan" .)