Regular occurrences of racial trouble (3)
I believe the answer is:
ail
'trouble' is the definition.
(synonyms)
'regular occurrences of racial' is the wordplay.
'regular occurrences of' indicates alternate letters (letters taken at regular intervals).
The alternate letters of 'racial' are 'AIL'.
(Other definitions for ail that I've seen before include "Worry" , "Trouble, afflict; be sickly" , "Be the worse for wear" , "pain" , "Go sick" .)