One born in Leeds upset French composer (7)
I believe the answer is:
delibes
'french composer' is the definition.
(I've seen this before)
'one born in leeds upset' is the wordplay.
'one' becomes 'i' (Roman numeral).
'born' becomes 'b'.
'in' is an insertion indicator.
'upset' indicates anagramming the letters.
'i'+'b'='ib'
'leeds' with letters rearranged gives 'deles'.
'ib' placed into 'deles' is 'DELIBES'.
(Other definitions for delibes that I've seen before include "French composer, Leo (1836-91)" , "Sylvia's French composer, 1836-91" , "Leo -, Coppelia composer" , "Lakme composer" .)