Chap to roam with? (4)

I believe the answer is:

omar

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'chap' is the definition.

'roam with?' is the wordplay.
'roam' anagrams to 'OMAR'.
But, I am not clear how the anagram is indicated.

'to' acts as a link.

Can you help me to learn more?

(Other definitions for omar that I've seen before include "- - Sharif (films)" , "- Sharif, film actor" , "- Khayyam, Persian poet, astronomer and mathematician" , "Arab" , "- Khayyam, Pers. poet" .)

I've seen this clue in the Evening Standard.

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