The most common and most likely answer to this crossword clue is the 5 letter word FIFTH
I've seen this crossword clue in The Daily Telegraph
F
I
F
T
H
More clues leading to the result FIFTH
- Garbage left abandoned staff finally collected in interval
- Some relief if there’s a musical interval
- You need some proof if this taken
- Couple short of place fit to accommodate fine horse
- Some relief, if thinking 27 quoted elsewhere
- This position from top twenty per cent
- Proportion of mud that’s fine for lake
Buddy explains!

The straight part
We know that "Proportion" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case proportion = fifth.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 FIFTH mean?
FIFTH noun- The person or thing in the fifth position.
- One of five equal parts of a whole.
- The fifth gear of an engine.
- A quantity of liquor equal to one-fifth of a gallon, or, more commonly, 750 milliliters (that is, three quarters of a liter).
- The musical interval between one note and another seven semitones higher (the fifth note in the major/minor scale)
- The fifth voice in a polyphonic melody.
- To support something fifth, after four others have already done so.
- To divide by 5, equates to multiplying a denominator by 5
- The ordinal form of the number five.