Bearers and cross-country runners using different leader (8)

I believe the answer is:
carriers
'bearers' is the definition.
('carrier' can be a synonym of 'bearer')
'cross-country runners using different leader' is the wordplay.
I cannot quite understand how this works, but
'runners' could be 'rr' (an abbreviation for runner written twice) and 'rr' is found in the answer.
This explanation may well be incorrect...
'and' acts as a link.
Can you help me to learn more?
I've seen this clue in The Times.
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