He’ll spill the beans on how to get kids to sleep (8)
I believe the answer is:
telltale
'he'll spill the beans on how to get kids to sleep' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he'll spill the beans on' is the wordplay.
'he'll' becomes 'tale' (I can't justify this - if you can you should believe this answer much more).
'spill the beans' becomes 'tell' (I've seen this in another clue).
'on' is a charade indicator (letters next to each other).
'tale' after 'tell' is 'TELLTALE'.
Can you help me to learn more?
(Other definitions for telltale that I've seen before include "Revelatory - blabbermouth" , "Person revealing secrets" , "Outward indication of something concealed" , "Person who gossips or blabs secrets" , "One spreads other people's secrets" .)