The most common and most likely answer to this crossword clue is the 5 letter word SPAHI
I've seen this crossword clue in The Guardian
S
P
A
H
I
More clues leading to the result SPAHI
Buddy explains!

The straight part
We know that "Cavalryman/Cavalryman" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cavalryman/cavalryman = spahi.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 SPAHI mean?
SPAHI noun- (history) An Ottoman (Turkish empire) cavalryman, especially as recruited under a land-based system.
- (history) A soldier in a mainly Arab-recruited cavalry (originally horse, later light armored) regiment in French colonial service in (former/ in name still) Ottoman North African provinces