Kind of wheel for light carriage (3)
I believe the answer is:
fly
'carriage' is the definition.
(I've seen this in other clues)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for fly that I've seen before include "needs to get away" , "Knowing, insect" , "One invited into parlour" , "Fishing insect" , "Insect; go quickly" .)