It's a slang term for unemployment benefit. That's somewhat confused these days because there isn't such a thing as unemployment benefit in the UK any more. There's "jobseeker's allowance", "income support", "housing benefit", "universal credit", and a few others, all of which can be claimed by people who are currently looking for work, or in work but on a low income, or who are unable to work. It's a confusing minefield designed to put people off claiming what they're legally entitled to.