Beast involved in Bataclan crime (8,5)
I believe the answer is:
bactrian camel
'beast' is the definition.
'involved in bataclan crime' is the wordplay.
'involved in' indicates anagramming the letters (involved can mean complex or confusing).
'bataclan'+'crime'='bataclancrime'
'bataclancrime' is an anagram of 'BACTRIAN CAMEL'.
(Other definitions for bactrian camel that I've seen before include "Two-humped creature" , "Two-humped animal" , "Humped animal" .)