One to be crossed with a goat (4)

I believe the answer is:

ibex

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

'a goat' is the definition.
(ibex is a kind of goat)

'one to be crossed' is the wordplay.
'one' becomes 'i' (Roman numeral).
'crossed' becomes 'x' (I can't explain this - if you can you should believe this answer much more).
'i'+'be'+'x'='IBEX'

'with' acts as a link.

Can you help me to learn more?

(Other definitions for ibex that I've seen before include "Sure-footed climber" , "Pyrenean mountain goat" , "one seldom puts a foot wrong" , "Wild goat with large recurved horns" , "Wild goat with double curved horns" .)

I've seen this clue in The Globe and Mail.

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.