The most common and most likely answer to this crossword clue is the 6 letter word STORES
I've seen this crossword clue in The Daily Telegraph
S
T
O
R
E
S
More clues leading to the result STORES
Buddy explains!

The straight part
We know that "Supplies" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case supplies = stores.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 STORES mean?
STORES noun- A place where items may be accumulated or routinely kept.
- A supply held in storage.
- (mainly North American) A place where items may be purchased; a shop.
- Memory.
- A great quantity or number; abundance.
- To keep (something) while not in use, generally in a place meant for that purpose.
- To write (something) into memory or registers.