The most common and most likely answer to this crossword clue is the 5 plus 5 letter word GHOST TRAIN
I've seen this crossword clue in Independent
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More clues leading to the result GHOST TRAIN
- Juggling not right, as entertainment frightening children
- Entertainer gets time in small part in fairground attraction
- Fair diversion leading straight on to crash?
- Ride straight on up the creek
- Ride straight on in error
- Move straight on for the scary ride
- Jumping straight on funfair ride
- Scary ride travelling straight on
- Sort hating bumpy fairground ride
Buddy explains!

The straight part
We know that "Fair diversion" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fair diversion = ghost train.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.