The most common and most likely answer to this crossword clue is the 14 letter word POLYSACCHARIDE
I've seen this crossword clue in The Times
P
O
L
Y
S
A
C
C
H
A
R
I
D
E
More clues leading to the result POLYSACCHARIDE
Buddy explains!

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 POLYSACCHARIDE mean?
POLYSACCHARIDE noun- A polymer made of many saccharide units linked by glycosidic bonds.