Top copy with a cross on (4)

I believe the answer is:

apex

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

'top' is the definition.
(apex is a top or peak)

'copy with a cross on' is the wordplay.
'copy with' becomes 'ape' (ape can mean to copy or imitate. I am not sure about the 'with' bit.).
'a cross' becomes 'x' (an X is a cross).
'on' is a charade indicator (letters next to each other).
'ape'+'x'='APEX'

Can you help me to learn more?

(Other definitions for apex that I've seen before include "The highest point of something" , "Tip -- top" , "climax" , "Point or summit" , "Apogee, summit" .)

I've seen this clue in the Evening Standard.

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.