Take on chief leading all-English league at last (9)
I believe the answer is:
challenge
'take' is the definition.
(thesaurus)
'chief leading all-english league at last' is the wordplay.
'chief' becomes 'ch' (I've seen this in other clues).
'leading' says to put letters next to each other.
'english' becomes 'eng'.
'at last' suggests the final letters.
The last letter of 'league' is 'e'.
'ch'+'all'+'eng'+'e'='CHALLENGE'
'on' is the link.
(Other definitions for challenge that I've seen before include "Dispute the truth of" , "Difficult undertaking" , "problem" , "Defy, confront" , "Demanding or stimulating situation" .)