Black dog coats produce shine — it's the local food (3,4)
I believe the answer is:
pub grub
'the local food' is the definition.
(I've seen this before)
'black dog coats produce shine' is the wordplay.
'black' becomes 'b' (abbreviation as in pencil classifications).
'dog' becomes 'pug' (pug is a kind of dog).
'coats' indicates putting letters inside (inserted letters are coated in another word).
'produce shine' becomes 'rub' (I can't justify this - if you can you should believe this answer much more).
'b' going within 'pug' is 'pubg'.
'pubg'+'rub'='PUB GRUB'
'it's' acts as a link.
Can you help me to learn more?
(Other definitions for pub grub that I've seen before include "Food served at a local" , "local courses" , "Food served in bars" , ""Dog and Duck" food" .)