Somehow halt Mo Farah before end of modern running event

I believe the answer is:

half-marathon

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'running event' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'somehow halt mo farah before end of modern' is the wordplay.
'somehow' indicates anagramming the letters.
'before' means one lot of letters go next to another.
'end of' suggests the final letters.
The last letter of 'modern' is 'n'.
'halt'+'mo'+'farah'='haltmofarah'
'haltmofarah' with letters rearranged gives 'halfmaratho'.
'halfmaratho'+'n'='HALF-MARATHON'

Can you help me to learn more?

(Other definitions for half-marathon that I've seen before include "Race of 13 miles 352 yards" , "Race of 21.243 km" .)

I've seen this clue in The Guardian.

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