Do I have to clean the property for the buyer before settlement?

As the seller of the property, you are obligated to provide to the buyer the property in the same condition as it was on the contract date. This means that if your property was clean and tidy when the contract was formed, then it also has to be delivered to the buyer in a reasonably clean state. This doesn’t necessarily mean that you need to arrange for professional cleaning of the property, unless you have specifically contracted to do so under a special condition of the contract.
In any case, to avoid a dispute with the buyer closer towards settlement date, you should try to clear the property at least the day before settlement and allow them to inspect the property. At least then you will have time to rectify any issues with the buyer prior to settlement. During your move out, you should also do what you can to avoid damage to the property, as damages caused during a move out is unlikely to be classified as fair wear and tear.