Monster gets money-bag out (8)
I believe the answer is:
bogeyman
'monster' is the definition.
(I know that bogeyman is a type of monster)
'money-bag out' is the wordplay.
'out' is an anagram indicator (out can mean wrong or inaccurate).
'money'+'bag'='moneybag'
'moneybag' with letters rearranged gives 'BOGEYMAN'.
'gets' is the link.
(Other definitions for bogeyman that I've seen before include "Imaginary monster to frighten children" , "Imaginary evil spirit, used to frighten children" , "Evil spirit frightening children" , "Imaginary male feared by children" , "Unpleasant character" .)