The most common and most likely answer to this crossword clue is the 11 letter word CHLOROPHYLL
C
H
L
O
R
O
P
H
Y
L
L
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 CHLOROPHYLL mean?
CHLOROPHYLL noun- Any of a group of green pigments that are found in the chloroplasts of plants and in other photosynthetic organisms such as cyanobacteria.