Equivalent figure in work to advance food additive (8,6)
I believe the answer is:
opposite number
'equivalent' is the definition.
(opposite number is a kind of equivalent)
'work to advance food additive' is the wordplay.
'work' becomes 'op' (common abbreviation for 'opus').
'to advance' becomes 'posit' (both can mean to put forward or suggest).
'food additive' becomes 'E number' (type of food additive).
'op'+'posit'+'enumber'='OPPOSITE NUMBER'
'figure in' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for opposite number that I've seen before include "colleague elsewhere" , "Counterpart" , "Direct competitor" , "One of similar status" , "pal!" .)