The most common and most likely answer to this crossword clue is the 6 letter word BATMAN
I've seen this crossword clue in The Guardian
B
A
T
M
A
N
More clues leading to the result BATMAN
- Cricketer losing heart becoming hero
- Comic book character, an officer's personal servant
- Grace, perhaps, but no heart — superhero!
- Military servant, disheartened cricketer
- Military aide to call back shortly after flyer
- Cricketer dismissing second officer’s servant
- Black hole in wall starts to alarm nervous attendant
- Cricketer that’s second out — Wayne, the night watchman?
- . . . . player number 4’s out to get the Saviour of Gotham
- Servant uses 2 in the 22 in common location, withdrawing large amount
Buddy explains!

The straight part
We know that "Military aide" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case military aide = batman.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 BATMAN mean?
BATMAN noun- A servant or valet to an army officer.
- (by extension) A personal assistant or supporter.
- To act as a batman.
- A unit of weight established in 1931 equal to 10 kg.
- A Turkish unit of weight varying by location, time, and item from 2–8 okas (about 2.5–10 kg).
- (mountaineering) To climb up or down a rope free hand (i.e. as Batman does).