Big cheese spread including old wine (9)
I believe the answer is:
potentate
'big cheese' is the definition.
(both can mean a ruler)
'spread including old wine' is the wordplay.
I cannot really understand how this works, but
'old' could be 'o' (common abbreviation eg in OE for Old English) and 'o' is located in the answer.
'wine' could be 'tent' (I've seen this before) and 'tent' is found in the answer.
'spread' could be 'pate' (pate is a kind of spread) and 'pate' is located in the leftover letters.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
(Other definitions for potentate that I've seen before include "A monarch or ruler" , "authority" , "Mogul" , "Powerful autocratic ruler" .)