be on a hiding to nothing
From Longman Dictionary of Contemporary Englishbe on a hiding to nothingbe on a hiding to nothingBritish English informalWASTE something to be completely wasting your time trying to do something → hidingExamples from the Corpusbe on a hiding to nothing• But he was on a hiding to nothing really.• Time was never called and the tide was soon to discover it was on a hiding to nothing.