Storer of cookies knowing to eat 500 (6)
I believe the answer is:
adware
'storer of cookies' is the definition.
I know nothing about this answer so I cannot tell whether this works.
'knowing to eat 500' is the wordplay.
'knowing' becomes 'aware' (I've seen this before).
'to eat' means one lot of letters goes inside another.
'500' becomes 'D' (Roman numeral for 500).
'aware' enclosing 'd' is 'ADWARE'.
Can you help me to learn more?
(Other definitions for adware that I've seen before include "computer plug-ins?" , "web advertising programs" , "computer programs" , "commercial apps" .)