The most common and most likely answer to this crossword clue is the 6 letter word LEARNS
I've seen this crossword clue in Financial Times
L
E
A
R
N
S
Buddy explains!

The straight part
We know that "is wiser" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case is wiser = learns.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 LEARNS mean?
LEARNS verb- To acquire, or attempt to acquire knowledge or an ability to do something.
- To attend a course or other educational activity.
- To gain knowledge from a bad experience so as to improve.
- To study.
- To come to know; to become informed of; to find out.
- To teach.