Crossword Genius

Fail to honour some pair (5,1,7)

Ross

I believe the answer is:

break a promise

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

'fail' is the definition.
I know nothing about this answer so I cannot tell whether this works.

'honour some pair' is the wordplay.
I cannot quite see how this works, but
'honour' could be 'om' and 'om' is found in the answer.
'some' could be 'a' and 'a' is located in the answer.
an anagram of 'pair' is 'apri' which is located in the left over letters.
This may be the basis of clue (or it may be nonsense).

'to' acts as a link.

Can you help me to learn more?

I've seen this clue in The Hindu.
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