Crossword Genius

Section of Matterhorn on own? Impossible (2-2)

Ross

I believe the answer is:

no-go

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

'impossible' is the definition.
(I've seen this before)

'section of matterhorn on own?' is the wordplay.
I cannot really see how this works, but
'of' could be 'o' and 'o' is found in the answer.
The remaining letters 'ngo' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for no-go that I've seen before include "Impossible task for goon" , "Hopeless (informal)" , "Prohibited area" , "Not possible, futile" , "Can't be done, not on" .)

I've seen this clue in The Telegraph.
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