The most common and most likely answer to this crossword clue is the 9 letter word SECRETION
I've seen this crossword clue in The Guardian
S
E
C
R
E
T
I
O
N
Buddy explains!

The straight part
We know that "Discharge" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case discharge = secretion.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 SECRETION mean?
SECRETION noun- Any substance that is secreted by an organism
- The act of secreting a substance, especially from a gland
- The act of hiding something