The most common and most likely answer to this crossword clue is the 5 letter word KOMBU
K
O
M
B
U
More clues leading to the result KOMBU
Buddy explains!

The straight part
We know that "Edible seaweed," is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case edible seaweed, = kombu.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 KOMBU mean?
KOMBU noun- Edible kelp (from the class Phaeophyceae) used in East Asian cuisine.