From Longman Dictionary of Contemporary Englishtune up phrasal verb1 APMwhen musicians tune up, they prepare their instruments to play at the right pitchtune something ↔ up The band were tuning up their guitars.2 tune something ↔ up to make small changes to an engine so that it works as well as possible → tune→ See Verb tabletune-upˈtune-up noun [singular] 1 TETTCthe process of making small changes to an engine so that it works as well as possible2 an occasion that someone uses as preparation for a more important occasion He is treating the semi-finals as a tune-up.
Examples from the Corpus
tune-up• If you give the engine regular tune-ups, it will last much longer.• Therefore, he is treating the semi-final trials more as a tune-up.• It's about time to take the car in for a tune-up again.• Perhaps the owner asked for a spiritual tune-up. 