Bloke heads north, overtaking first of young African runners (5)
I believe the answer is:
nyala
'african runners' is the definition.
(nyala are a type of antelope known for running)
'bloke heads north overtaking first of young' is the wordplay.
'bloke heads' becomes 'alan' (I can't justify this - if you can you should give a lot more credence to this answer).
'north' says the letters should be written backwards (in a down clue, letters go up or 'northward').
'overtaking' indicates putting letters inside (a word 'takes over' another set of letters).
'first of young' becomes 'y' (ast letter of 'young').
'alan' back-to-front is 'nala'.
'nala' enclosing 'y' is 'NYALA'.
Can you help me to learn more?
(Other definitions for nyala that I've seen before include "South African antelope - Sudanese city" , "South African resident" , "one of a herd" , "crested antelope" , "Spiral-horned antelope" .)