The most common and most likely answer to this crossword clue is the 4 letter word OMER
I've seen this crossword clue in The Times
O
M
E
R
Buddy explains!
The straight part
We know that "Measure" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case measure = omer.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 OMER mean?
OMER noun- A former small Hebrew unit of dry volume equal to about 2.3 L or 2.1 quarts.
- A vessel of one omer.
- The sheaf of barley offered on the second day of Passover.
- The counting of the omer, that is, the period of 49 days between Passover and Shavuot.