End outside review regularly taken for bank’s action to support currency (12)
I believe the answer is:
intervention
'end' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe you can see an association between them that I don't see?
I cannot understand how the remainder of the clue works.
(Other definitions for intervention that I've seen before include "Agency" , "Mediation; interference" , "Action taken to improve a medical disorder" , "Mediation, stepping-in" .)