An idiom is a group of words, or in other words, a phrase that has a meaning other than its literal meaning of the words in it.
fix up (something) or fix (something) up
to repair something, to put something back in good condition
We want to fix up our house this summer.
List of common idioms, their meanings and examples of their usage in sentences
An idiom is a type of phrase or expression that has a meaning that can't be deciphered by defining the individual words.