It's not a new usage by any means. Like almost all slang it originated with Black drag and LGBT+ subcultures and only semi-recently (within the last 10-15 years maybe?) broke containment in the US.
As a verb, "to clock" means something like "to notice" or maybe in this case "to highlight, with specificity".
As a verb, "to clock" means something like "to notice" or maybe in this case "to highlight, with specificity".