A backcloth is a large piece of cloth, often with scenery or buildings painted on it, that is hung at the back of a stage while a play is being performed. [British]
regional note: in AM, use backdrop
2. singular noun
The backclothof an event is the general situation in which it happens. [British, journalism, literary]
...the promise of tax cuts against the backcloth of a public-spending deficit. [+ of]