Answer:
An allusion.
Explanation:
An allusion is a literary device or figurative language that writers use to bring forth an expression about something in particular, but not explicitly mentioning it. It is like giving an example of something without directly referring to it.
The given excerpt from "My First March", the author refers to how a group of people began singing a song about "heatwave" which is a reference to the hot and scorching nature of the present situation. This is an allusion to the weather of the place, with the song's title an allusion to the weather.
