They reflect as lion, say, moans audibly (4-4)
I believe the answer is:
'they reflect' is the definition.
(cat's-eyes are reflective road features)
'lion say moans audibly' is the wordplay.
I cannot really see how this works, but
'lion' could be 'cat' (lions are big cats) and 'cat' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'as' is the link.
Can you help me to learn more?
(Other definitions for cats-eyes that I've seen before include "Light-reflecting studs set into road" , "Reflecting devices embedded in roads" , "Line of reflective studs as road markings- very feline" , "Road safety devices" , "Middle-of-the-road reflectors" .)