Warning sheep had to listen to (3,4)
I believe the answer is:
you wait
'warning' is the definition.
('just you wait!')
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for you wait that I've seen before include "there will be trouble" , "Threat" , "sounds threatening" , "Words of warning" , "When service is slow" .)