Races round in fright (5)
I believe the answer is:
scare
'fright' is the definition.
(I know that fright can be written as scare)
'races round' is the wordplay.
'round' indicates anagramming the letters.
'races' is an anagram of 'SCARE'.
'in' acts as a link.
(Other definitions for scare that I've seen before include "Health worry" , "Frighten or intimidate" , "Greatly frighten" , "Startle" , "Panic" .)