The French sang about English dish (7)
I believe the answer is:
lasagne
'dish' is the definition.
(lasagne is a kind of dish)
'the french sang about english' is the wordplay.
'the french' becomes 'la' (one of the French words for 'the').
'about' indicates anagramming the letters.
'english' becomes 'E' (abbreviation).
'sang' is an anagram of 'sagn'.
'la'+'sagn'+'e'='LASAGNE'
(Other definitions for lasagne that I've seen before include "Layered pasta dish" , "Lea sang out for the pasta dish" , "Italian dish with layers of pasts and mince between" , "Type of pasta" , "Italian sheets" .)