No, it’s a metaphor. Maybeee metaphor mixed with a double entendre. But not an idiom. Idioms are established by common usage, like it’s “raining cats and dogs.” Since this isn’t a common expression, it’s not an idiom. It’s closer to a double entendre, but in the way that metaphors are—both have double meanings. The difference between a double entendre and a metaphor, is that a DE is more like a pun but phrase-length (saying a busy track star has been “running a mile a minute,” which refers to both their speed as a track star and being busy in day to day life), and more often has a sexual double meaning (“try his meat, emily” when a sexy chef cooks a steak especially for a customer—lol Emily in Paris). A metaphor, however, expresses an idea, often an abstract one, using some sort of parallel concept. Like “He was my flower and I helped him grow” or something.