European left darts having bagged 500 doubles in separate legs (8)
I believe the answer is:
straddle
'separate legs' is the definition.
(to straddle is put one's legs around something)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for straddle that I've seen before include "noncommittal stance" , "Get over" , "Bestride" , "jumping technique" , "Have one leg on each side of" .)