Battle remembered in the long run (8)
I believe the answer is:
marathon
This might be a double definition.
'battle remembered in' is the first definition.
'Marathon' can be an answer for 'battle' (Battle of Marathon, 490 BC). I am not sure about the 'remembered in' bit.
'long run' is the second definition.
(long-distance run)
'the' acts as a link.
Can you help me to learn more?
(Other definitions for marathon that I've seen before include "Pheidippides' starting point" , "Long distance race" , "Footrace of 26 miles 385 yards" , "strenuous event" , "Long-distance foot race" .)