A word twice back at leaving (2-2)
I believe the answer is:
ta-ta
'a word' is the definition.
Both the definition and answer are singular nouns.
Maybe there's an association between them I don't understand?
'twice back at leaving' is the wordplay.
I cannot quite understand how this works, but
'at' is found in the answer.
The remaining letters 'ta' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for ta-ta that I've seen before include "Adieu" , "A Farewell" , "Cheerio" , "Bye-bye" , "Bye!" .)