The most common and most likely answer to this crossword clue is the 11 letter word GENERALSHIP
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The straight part
We know that "skill in military command" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case skill in military command = generalship.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.
Crossword Answer definitions
GENERALSHIP noun- The position or office of a general.
- The term of office of a military general.
- The skills or performance of a good general; military leadership, strategy.
- By extension, leadership, good management.