The most common and most likely answer to this crossword clue is the 5 letter word BURSA
I've seen this crossword clue in The Guardian
B
U
R
S
A
More clues leading to the result BURSA
Buddy explains!
The straight part
We know that "pouch" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case pouch = bursa.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 BURSA mean?
BURSA noun- Any of the many small fluid-filled sacs located at the point where a muscle or tendon slides across bone. These sacs serve to reduce friction between the two moving surfaces.