Young flyers, say, holding adult licences (7)
I believe the answer is:
eaglets
'young flyers' is the definition.
Although both the answer and definition are plural nouns, I can't see how they can define each other.
'say holding adult licences' is the wordplay.
'say' becomes 'eg' (both can mean 'for example').
'holding' indicates putting letters inside.
'adult' becomes 'a' (abbreviation).
'licences' becomes 'lets' (I can't explain this - if you can you should believe this answer much more).
'eg' enclosing 'a' is 'eag'.
'eag'+'lets'='EAGLETS'
Can you help me to learn more?
(Other definitions for eaglets that I've seen before include "birds early in life" , "Small birds" .)