The most common and most likely answer to this crossword clue is the 13 letter word QUARTERMASTER
I've seen this crossword clue in The Sunday Telegraph
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More clues leading to the result QUARTERMASTER
Buddy explains!
The straight part
We know that "Person in charge of military supplies" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case person in charge of military supplies = quartermaster.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 QUARTERMASTER mean?
QUARTERMASTER noun- An officer whose duty is to provide quarters, provisions, storage, clothing, fuel, stationery, and transportation for a regiment or other body of troops, and superintend the supplies.
- A petty officer who attends to the helm, binnacle, signals, and the like, under the direction of the master.