They fly although they are pwerless to do so (7)
I believe the answer is:
gliders
'they' is the definition.
Both the definition and answer are plural nouns.
Perhaps there's an association between them I don't understand?
'fly although they are pwerless to do so' is the wordplay.
I cannot really understand how this works, but
'fly' could be 'glide' (gliding is a kind of flying) and 'glide' is located 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 gliders that I've seen is " Flying vehicles without engines".)