Ready to attack claim ex is now racist periodically (3,2,4)
I believe the answer is:
lie in wait
'ready to attack' is the definition.
I don't know anything about this answer so I can't judge whether this works.
'claim ex is now racist periodically' is the wordplay.
'periodically' indicates alternate letters (letters must be selected 'every so often').
'claim'+'ex'+'is'+'now'+'racist'='claimexisnowracist'
The alternate letters of 'claimexisnowracist' are 'LIE IN WAIT'.
Can you help me to learn more?
(Other definitions for lie in wait that I've seen before include "what will hunter do?" , "Be prepared to ambush" , "Prepare to attack" , "Hope to catch" , "hover" .)