The most common and most likely answer to this crossword clue is the 15 letter word WINNIE-THE-POOH
W
I
N
N
I
E
-
T
H
E
-
P
O
O
H
Buddy explains!
The straight part
We know that "Bear" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bear = winnie-the-pooh.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.