The most common and most likely answer to this crossword clue is the 5 plus 7 letter word CROSS COUNTRY
I've seen this crossword clue in The Daily Telegraph
C
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O
S
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C
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More clues leading to the result CROSS COUNTRY
Buddy explains!
The straight part
We know that "Running event" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case running event = cross country.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does CROSS COUNTRY mean?
CROSS COUNTRY noun- A running sport popular in US high schools, colleges, etc. where participants race over varying terrain (e.g. golf courses, roads, etc.) in approximately 5- to 10-kilometre races. Abbreviated XC.
- A phase of the equestrian sport of three day eventing, which the horse and rider travel over varied terrain and jump natural obstacles.
- Flight between two points or aerodromes using navigational techniques.
- From one side of a country to the other.
- Across countryside.
- Relating to cross country racing.
- (of data or research) Across countries.