Extra lap makes participants run back across African city (7)
I believe the answer is:
kampala
'african city' is the definition.
(capital of Uganda)
'extra lap makes participants run back across' is the wordplay.
'across' says the answer is hidden in the clue.
'run back' says the letters should be written in reverse (I've seen 'running back' mean this).
'alapmak' is hidden within 'extra lap makes participants'.
'alapmak' backwards is 'KAMPALA'.
(Other definitions for kampala that I've seen before include "in East Africa" , "Capital of Uganda" , "Ugandan city" , "Ugandan capital" , "Uganda's capital" .)