Is it for a clock?

Am I alone for not getting this?

For anyone who doesn’t get it:

For a clock sounds like for a cock, the joke is that the cashier is joking that the customer need to know when its cock o clock. He jokes this because the customer is gay and the cashier is homophobic.

These are my favorite kind of meme because it’s really funny stupid humor, but also I feel really smart when I open the comments and see people trying to figure out what it means