Island cycling feature (4)

I believe the answer is:
chin
This clue might be a double definition.
'island cycling' is the first definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'feature' is the second definition.
(facial feature)
Can you help me to learn more?
(Other definitions for chin that I've seen before include "Front of lower jaw" , "Outstanding jaw part" , "hit" , "Feature of face" , "Bottom part of jaw" .)
