This is a charade - two separate parts are joined together to form the answer. Look for how the clue breaks into different components that combine.
The clue splits into two parts: 'Settle' gives you the first part (think about settling a bill), and 'where stated' gives you the second part - 'stated' is the homophone indicator, so you need a word that sounds like 'where'.
Answer: FOOTWEAR | 'Settle' means FOOT (as in foot the bill), plus WEAR sounds like 'where' (indicated by 'stated'). Oxford and Derby are types of shoes, which is footwear.