The most common and most likely answer to this crossword clue is the 9 letter word STOCKPILE
S
T
O
C
K
P
I
L
E
Buddy explains!
The straight part
We know that "Keep" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case keep = stockpile.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 STOCKPILE mean?
STOCKPILE noun- A supply, especially a large one, of something kept for future use.
- To accumulate a stockpile.