One cat got going immediately (2,4)
I believe the answer is:
at once
'immediately' is the definition.
(I've seen this before)
'one cat got going' is the wordplay.
'one cat' can be anagrammed to 'AT ONCE'.
However, I am unsure how this is indicated.
Can you help me to learn more?
(Other definitions for at once that I've seen before include "'Immediately (2,4)'" , "'Without delay (2,4)'" , "on the spot" , "Instantly" , "without hesitation" .)