The most common and most likely answer to this crossword clue is the 4 letter word SLIM
I've seen this crossword clue in The Daily Telegraph
S
L
I
M
More clues leading to the result SLIM
Buddy explains!

The straight part
We know that "Wartime general" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case wartime general = slim.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 SLIM mean?
SLIM noun- A type of cigarette substantially longer and thinner than normal cigarettes.
- A potato farl.
- AIDS, or the chronic wasting associated with its later stages.
- Cocaine.
- To lose weight in order to achieve slimness.
- To make slimmer; to reduce in size.
- Slender, thin.
- (of something abstract like a chance or margin) Very small, tiny.
- (rural) Bad, of questionable quality; not strongly built, flimsy.
- Sly, crafty.