There thousands of fetishes, some more common than others. Foot fetish, watersports and crossdressing are incredibly common nowadays, and 1 in 3 people get sexually aroused by one of these acts.
A fetish could be anything, from cotton wool to whips and chains, it is just something that sexually excites a person that isn’t run of the mill sex.
Most escorts are open to fetishes; however, you always need to discuss with them first, don't just assume they will be ok with everything. Things like Hard sports are incredibly rare to find, so you will need to ask without causing offence.
If you have a particular clothing fetish, it's important you provide what is needed, the escort will not provide the materials for your kink.
It's important to always think of hygiene and safety first with whatever you have in mind.