Nuts in AA to meet separately (3,2,1,4)
I believe the answer is:
one at a time
'separately' is the definition.
Both the answer and definition are adverbs. Perhaps you can see an association between them that I can't see?
'nuts in aa to meet' is the wordplay.
'nuts' indicates anagramming the letters (nuts can mean crazy).
'in'+'aa'+'to'+'meet'='inaatomeet'
'inaatomeet' anagrammed gives 'ONE AT A TIME'.
Can you help me to learn more?
(Other definitions for one at a time that I've seen before include "Individually" , "Singly" , "A-team, I note, travelling separately" .)