The most common and most likely answer to this crossword clue is the 5 letter word GRIST
I've seen this crossword clue in The Times
G
R
I
S
T
More clues leading to the result GRIST
- Milling corn gerbils ate regularly
- Corny stuff in act Sir Galahad served up
- What’s ground for girls to be unhappy, dropping Latin at beginning of term
- What’s to be ground by King George I?
- Philosopher follows main point about run — it’s grinding
- In essence, miller’s conclusion it’s what he needs
- What is ground in the middle flooded by river
- Meaning to cross river for grain
Buddy explains!

The straight part
We know that "Milling corn" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case milling corn = grist.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 GRIST mean?
GRIST noun- Grain that is to be ground in a mill.
- A group of bees.
- Supply; provision.
- (ropemaking) A given size of rope, common grist being a rope three inches in circumference, with twenty yarns in each of the three strands.