The most common and most likely answer to this crossword clue is the 10 letter word BATTLE-AXE
I've seen this crossword clue in The Times
B
A
T
T
L
E
-
A
X
E
Buddy explains!
The straight part
We know that "Dragon slayer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dragon slayer = battle-axe.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 BATTLE-AXE mean?
BATTLE-AXE noun- An ancient military weapon, an axe designed for combat.
- This weapon borne on arms as a mark of prowess.
- A domineering, antagonistic woman.
- An electric guitar.
- (usually spelt "battleaxe") An allotment of land at the rear of another property, with a long, narrow strip of land connecting it to the roadway.