Blue ones are fine! (5)
I believe the answer is:
skies
'blue ones' is the definition.
Although both the answer and definition are plural nouns, I don't see how one could define the other.
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for skies that I've seen before include "Heavens" , "Hits high in the air" .)