Sounds like children's author demanded money (6)
I believe the answer is:
ransom
'demanded money' is the definition.
(money demanded by a kidnapper)
'sounds like children's author' is the wordplay.
'sounds like' shows a homophone (sound like).
'children's author' becomes 'ransome' (Swallows and Amazons author Arthur Ransome).
'ransome' is a homophone of 'RANSOM'.
(Other definitions for ransom that I've seen before include "Money demanded for the release of someone" , "Fee for kidnap release" , "Payment, eg to kidnapper" , "Kidnapper's payoff" , "Rescue" .)