Fly eternally over the backblocks (5-5,4)
I believe the answer is:
never-never land
'fly' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'eternally over the backblocks' is the wordplay.
I cannot really see how this works, but
'eternally' could be 'ever' (I've seen this before) and 'ever' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for never-never land that I've seen is " Imaginary country (Peter Pan)".)