Say, hardly fast food! (4)
I believe the answer is:
sloe
'say' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'hardly fast food' is the wordplay.
'hardly fast' becomes 'slo' (I can't explain this - if you can you should believe this answer much more).
'food' becomes 'E' (E is an example).
'slo'+'e'='SLOE'
Can you help me to learn more?
(Other definitions for sloe that I've seen before include "Fruit of the blackthorn does't sound fast" , "Blackthorn, used in making a type of gin" , "Fruit often used for gin" , "Sour blue-black fruit" , "Fruit steeped in gin to make a liqueur" .)