Evergreen filling fool with glee, oddly (7)

I believe the answer is:

ageless

I'm a little stuck... Click here to teach me more about this clue!

'evergreen' is the definition.
(evergreen can mean ageless or fresh)

'filling fool with glee oddly' is the wordplay.
'filling' means one lot of letters goes inside another.
'fool with' becomes 'ass' (both can mean a stupid person. I am not sure about the 'with' bit.).
'oddly' is an anagram indicator (letters in an odd order).
'glee' with letters rearranged gives 'gele'.
'ass' going around 'gele' is 'AGELESS'.

Can you help me to learn more?

(Other definitions for ageless that I've seen before include "Lasting forever" , "not appearing to get old" , "Staying young" , "Eternal - like Peter Pan" , "Eternally young" .)

I've seen this clue in The Daily Express.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.