The most common and most likely answer to this crossword clue is the 3 plus 4 letter word PRO RATA
I've seen this crossword clue in The Guardian
P
R
O
R
A
T
A
More clues leading to the result PRO RATA
- Men, splitting apart, strangely maintaining correspondence
- A raptor and a parrot remarkably commensurate
- Reason for arse needing one in proportion
- Alternative offered in a part exchange is equitable
- Article supporting publicity or thanks respectively
- A parrot, variegated correspondingly
- First to oust this person, American getting cheers, relatively speaking?
- Proportionately based voting system? Men answer with cheers
- A fair way of rewarding all involved in training a parrot
- For a sailor getting a raise, equitably distributed?
Buddy explains!

The straight part
We know that "commensurate" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case commensurate = pro rata.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 PRO RATA mean?
PRO RATA adverb- (of an allocation) In proportion to some factor that can be exactly calculated.