Bedlam as Charles invests zero (5)
I believe the answer is:
chaos
'bedlam' is the definition.
(I know that bedlam can be written as chaos)
'charles invests zero' is the wordplay.
'charles' becomes 'Chas' (shortened form).
'invests' indicates putting letters inside (inserted letters are invested).
'zero' becomes 'O' (O resembles 0).
'chas' enclosing 'o' is 'CHAOS'.
'as' is the link.
(Other definitions for chaos that I've seen before include "Bedlam" , "Complete disorder and confusion" , "State of extreme confusion and disorder" , "Totally disordered state" , "Utter confusion" .)