Boy and aunt get together in cheerful fashion (7)
I believe the answer is:
buoyant
'get together in cheerful fashion' is the definition.
I can't judge whether this defines the answer.
'boy and aunt' is the wordplay.
'boy' becomes 'ant' (I have seen 'Little boy' mean 'ant' so perhaps 'boy' could also mean 'ant').
'and' says to put letters next to each other.
'aunt' becomes 'buoy' (I can't justify this - if you can you should believe this answer much more).
'ant' after 'buoy' is 'BUOYANT'.
Can you help me to learn more?
(Other definitions for buoyant that I've seen before include "Animated or floating" , "Lively nineteen twenties dance" , "Floatable" , "Able to float" , "refusing to go to bed?" .)