Bottom to thrash in confused situation (6)
I believe the answer is:
'confused situation' is the definition.
(Bedlam can mean a state of chaos or madness)
'bottom to thrash' is the wordplay.
'bottom' becomes 'bed' (synonyms).
'to thrash' becomes 'lam' (both can mean to hit).
'in' is the link.
(Other definitions for bedlam that I've seen before include "Loud confused noise" , "Blamed for deafening noise" , "Blammed for uproar" , "Mayhem" , "State of extreme confusion and disorder" .)