From Longman Dictionary of Contemporary Englishgo sparego spareBritish English informalANGRYWORRIED to become very angry or worried Dad would go spare if he found out. → spare
Examples from the Corpus
go spare• I often ring at this time of the night for a chat, it helps to stop me from going spare.• Mrs Mangle would be mortified, Harold horrified ... and Scott would go spare.• So 10,000 posters are going spare, and the Tories are laughing.• One spare nut on a table may not seem much of an asset, but 10,000 nuts going spare are a liability. 