Head cook, revolutionary with top food (4)
I believe the answer is:
chef
'head cook' is the definition.
(I've seen this in another clue)
'revolutionary with top food' is the wordplay.
'revolutionary' becomes 'Che' (Che Guevara the Marxist revolutionary).
'with' means one lot of letters go next to another.
'top' indicates taking the first letters (in a down clue, the first letter is top).
The initial letter of 'food' is 'f'.
'che'+'f'='CHEF'
(Other definitions for chef that I've seen before include "Saucier" , "Hotel cook" , "member of kitchen staff" , "One who prepares courses" , "Cooker?" .)