Left in hacienda cooking a Mexican dish (9)
I believe the answer is:
enchilada
'a mexican dish' is the definition.
(I've seen this before)
'left in hacienda cooking' is the wordplay.
'left' becomes 'l' (common abbreviation).
'in' means one lot of letters goes inside another.
'cooking' is an anagram indicator.
'hacienda' anagrammed gives 'enchiada'.
'l' going inside 'enchiada' is 'ENCHILADA'.
(Other definitions for enchilada that I've seen before include "Hot food" , "Filled tortilla served with chilli sauce" , "spicy titbit" , "Tortilla and chilli dish" , "Rolled stuffed tortilla with chilli sauce" .)