Rue crashing out of the race, say (5)
I believe the answer is:
utter
'say' is the definition.
(to utter something is to speak or say it)
'rue crashing out of the race' is the wordplay.
'crashing' is an anagram indicator.
'out of' is an insertion indicator (some letters on the outside of others).
'the race' becomes 'tt'.
'rue' is an anagram of 'uer'.
'uer' placed around 'tt' is 'UTTER'.
(Other definitions for utter that I've seen before include "Express; complete" , "Dead" , "Say; total" , "Express audibly" , "Pronounce - total" .)