Counted 500th episode then finished (8)
I believe the answer is:
depended
'counted 500th episode' is the definition.
I can't judge whether this definition defines the answer.
'then finished' is the wordplay.
'then' becomes 'dep' (I am not sure about this - if you are sure you should believe this answer much more).
'finished' becomes 'ended' ('end' can be a synonym of 'finish').
'dep'+'ended'='DEPENDED'
Can you help me to learn more?
(Other definitions for depended that I've seen before include "Was conditional" , "Rested" , "Relied or hung on" .)