The most common and most likely answer to this crossword clue is the 4 letter word GRUB
I've seen this crossword clue in Financial Times
G
R
U
B
Buddy explains!
The straight part
We know that "Dig/food served in a pub" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dig/food served in a pub = grub.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does GRUB mean?
GRUB noun- An immature stage in the life cycle of an insect; a larva.
- Food.
- A short, thick man; a dwarf.
- A dirty person.
- A despicable person; a lowlife.
- To scavenge or in some way scrounge, typically for food.
- To dig; to dig up by the roots; to root out by digging; often followed by up.
- To supply with food.
- To eat.