This is keeping nothing for the lions (6)
I believe the answer is:
heroes
'the lions' is the definition.
The answer and definition can be both people as well as being plural nouns.
Perhaps there's an association between them I don't understand?
'this is keeping nothing' is the wordplay.
'this is' becomes 'here's' (both can be used to point out someone or something).
'keeping' indicates putting letters inside (some letters kept inside).
'nothing' becomes 'O' (looks like zero - 0).
'heres' going around 'o' is 'HEROES'.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for heroes that I've seen before include "Cavaliers" , "Brave people" , "Men of courage, chief characters in plays" , "Men of distinguished bravery and strength" , "Very brave men" .)