39d - straight clue (but &lit) 4 letters for 'food' in the general sense around the obvious letter.
8d - The French town is 4 letters and goes around an Indian dress (the longer spelling) but with an extra letter followed by the middle letter of... [def is medical].
15d - 'dusty' means it's archaic, next two words for the def - 'region' (4 letters) is shortened but also has an extra letter and 'inch' is a particular Scottish island.