From Longman Dictionary of Contemporary Englishelbow greaseelbow greaseinformalWORK HARD hard work and effort, especially when cleaning or polishing something → elbow
Examples from the Corpus
elbow grease• Pioneering vision is required, and elbow grease!• Cleaning Thanks to the availability of steam, cleaning is now a simple task, taking very little effort and no elbow grease.• Hopefully, this knowledge will save many householders a great deal of elbow grease!• It certainly saved a lot of elbow grease.• I give the pink botty a thorough good scrub, putting in plenty of elbow grease.• You'll need to use some elbow grease to get that floor clean. 