The most common and most likely answer to this crossword clue is the 6 letter word CAUSES
I've seen this crossword clue in The Guardian
C
A
U
S
E
S
More clues leading to the result CAUSES
Buddy explains!
The straight part
We know that "Reasons" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case reasons = causes.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 CAUSES mean?
CAUSES noun- (often with of, typically of adverse results) The source of, or reason for, an event or action; that which produces or effects a result.
- (especially with for and a bare noun) Sufficient reason for a state, as of emotion.
- A goal, aim or principle, especially one which transcends purely selfish ends.
- Sake; interest; advantage.
- Any subject of discussion or debate; a matter; an affair.
- A suit or action in court; any legal process by which a party endeavors to obtain his claim, or what he regards as his right; case; ground of action.
- To set off an event or action.
- (ditransitive) To actively produce as a result, by means of force or authority.
- To assign or show cause; to give a reason; to make excuse.