Sporty cyclist's end in ethical upset (8)
I believe the answer is:
Here is my best explanation:
'sporty' is the definition.
(I've seen this before)
'cyclist's end in ethical upset' is the subsidiary indication.
'end' says to take the final letters.
'in' indicates putting letters inside.
'upset' indicates anagramming the letters.
The last letter of 'cyclist' is 't'.
'ethical' with letters rearranged gives 'athleic'.
't' going within 'athleic' is 'athletic'.
(Other definitions for athletic that I've seen before include "Good at running and jumping", "With a strong and well proportioned body", "Given to partaking in sporting events", "Muscular", "Strong and active, good at sports", "Sporty, fit", "Lithe act (anag)", "Vigorous", "Lithe cat (anag.)" and "Strong and sporty".)