The most common and most likely answer to this crossword clue is the 8 letter word SUGGESTS
I've seen this crossword clue in The Daily Telegraph
S
U
G
G
E
S
T
S
Buddy explains!

The straight part
We know that "proposes" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case proposes = suggests.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 SUGGESTS mean?
SUGGESTS verb- To imply but stop short of saying explicitly.
- To make one suppose; cause one to suppose (something).
- To mention something as an idea, typically in order to recommend it
- To seduce; to prompt to evil; to tempt.