An idiom is defined as - a group of words in a fixed order that has a particular meaning that is different from the meanings of each word on its own.
Idiom:
set one's sights on (something)
Meaning:
to select something as one's goal
Example:
The local politician has set his sights on being elected to a higher office.
List of common idioms, their meanings and examples of their usage in sentences
An expression in the usage of a language that is peculiar to itself either in having a meaning that cannot be derived from the conjoined meanings of its elements or in its grammatically atypical use of words.