The most common and most likely answer to this crossword clue is the 9 letter word CORNFLOUR
I've seen this crossword clue in The Guardian
C
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More clues leading to the result CORNFLOUR
Buddy explains!
The straight part
We know that "Milled grain for a bloomer/ say" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case milled grain for a bloomer/ say = cornflour.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 CORNFLOUR mean?
CORNFLOUR noun- A very fine starch powder derived from maize (US corn) used in cooking as a thickener, to keep things from sticking, or as an anti-caking agent.