Can you wear a tampon for discharge?

No, tampons should only be used during menstruation.

Vaginal discharge is how your vagina keeps itself clean and it protects vaginal tissues, preventing discharge leaving your vagina traps bacteria within the vagina and tampons allow that bacteria to thrive, without menstrual flow tampons will dry-out vaginal tissues causing damage. This damage to vaginal walls allow bacterial toxins responsible for TSS direct access to the bloodstream so increases the risk of TSS. If you need to use something for discharge use cloth pantiliners.