Legendary king with weapon beating sword, battle-axe (9)
I believe the answer is:
pendragon
'legendary king' is the definition.
(I know that Pendragon is a type of legendary king)
'with weapon beating sword battle-axe' is the wordplay.
'with' is a charade indicator (letters next to each other).
'weapon beating sword' becomes 'pen' (the pen is mightier than the sword).
'battle-axe' becomes 'dragon' (I've seen this before).
'pen' put next to 'dragon' is 'PENDRAGON'.
(Other definitions for pendragon that I've seen before include "King Arthur, for example" , "old British chief" , "Uther --" , "Tribal chief," , "Ruler" .)