Bad Ben unexpectedly being arrested (6)
I believe the answer is:
nabbed
'being arrested' is the definition.
(I've seen this before)
'bad ben unexpectedly' is the wordplay.
'unexpectedly' indicates an anagram.
'bad'+'ben'='badben'
'badben' with letters rearranged gives 'NABBED'.
(Other definitions for nabbed that I've seen before include "Arrested" , "Seized suddenly" , "Caught someone doing something wrong" , "Caught (in the act)" .)