Error - mile run fast (8)
I believe the answer is:
misprint
'error' is the definition.
(misprint is a kind of error)
'mile run fast' is the wordplay.
'mile' becomes 'mi' (synonyms).
'run fast' becomes 'sprint' (I've seen this before).
'mi'+'sprint'='MISPRINT'
(Other definitions for misprint that I've seen before include "Typing error" , "mistake" , "could make sinners of the winners!" , "Type of slip" , "Possibly the wrong character" .)