Airlines will, in most cases, offer an amount which you can spend to cover the purchase of emergency clothing. Different airlines have different amounts, based on their policy (which usually includes length of time for the delay, whether you are at your home port or outstation, and may be higher for premium cabins).

Some airline will advise their limit automatically (at the time you fill out the lost luggage report), others will only tell you if you ask. If you don't ask at the airport, you can contact the airline once at your hotel to ask if you are entitled, and what their limit is.

Keep all receipts up to the airline's limit, and further receipts for claiming against travel insurance (if you have it).