Lesson in cooking shin and leg (7)
I believe the answer is:
english
'lesson' is the definition.
(English is a school subject)
'cooking shin and leg' is the wordplay.
'cooking' is an anagram indicator.
'and' is a charade indicator (letters next to each other) (I've seen this in other clues).
'shin' put after 'leg' is 'legshin'.
'legshin' anagrammed gives 'ENGLISH'.
'in' acts as a link.
(Other definitions for english that I've seen before include "The nationality in his glen" , "See 10" , "An official language of the Republic of India" , "Language spoken in his glen, strangely" , "Tongue" .)