Advertising for food, sounding fed up (8,5)
I believe the answer is:
sandwich board
'advertising' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'food sounding fed up' is the wordplay.
'food' becomes 'sandwich' (sandwich is a kind of food).
'sounding' shows a homophone (sound like).
'fed up' becomes 'bored' (fed up can mean bored).
'bored' is a homophone of 'board'.
'sandwich'+'board'='SANDWICH-BOARD'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for sandwich board that I've seen before include "Ad-carrier strapped on" , "Advertising hoarding carried up and down a street" , "Mobile advertising carrier" , "Advertisement carried up and down the street" , "something used for advertising" .)