Never-ending struggle on athletics track? (7,6)
I believe the answer is:
running battle
'never-ending struggle' is the definition.
(a running battle is a long-running confrontation)
'on athletics track?' is the wordplay.
I cannot quite understand how this works, but
'on' could be 'at' (I've seen this in other clues) and 'at' is found within the answer.
'athletics' could be 'running' (running is a kind of athletics) and 'running' is present in the answer.
This explanation may well be incorrect...
(Other definitions for running battle that I've seen before include "Military engagement whilst on the move" , "indecisive skirmish" , "Continuing skirmish" , "Fight carrying on continuously" , "Continuing feud" .)