elbow grease 
noun [mass noun] informal
Hard physical work, especially vigorous polishing or cleaning: nothing would shift it however much elbow grease we used...
- But hours of hard work and elbow grease transformed the shack into a bright, clean and well-stocked shop.
- With some hard work and elbow grease, the building was cleaned, painted, and filled with many shelves of books.
- Then, as if passing through some kind of barrier, there's nothing quite so important as the lavish application of elbow grease until my small kingdom is bright and sparkly again.
Synonyms
hard work, work, labour, toil, exertion, effort, slog, drudgery;
industry
informal grind, sweat, donkey work, spadework
British informal graft, fag
Australian/New Zealand informal yakka
archaic travail, moil