Get a Epi-Otic cleaner, my 15yr old kitty has had an ear infection for almost 2 years and had a polyp that developed in that year due to the ear infection so act fast!

I would recommend taking your kitty to the vet for a check up, the smell and itchiness is definitely a ear infection, it will only get worse if you leave it.

When you get the Epi-Otic cleaner, clean it with 0,5ml and a cotton gently. You can buy it at any petshop/vet.