Leaving word poor quality stuff is at start of auction (2-2)
I believe the answer is:
ta-ta
'leaving word' is the definition.
The definition suggests a singular noun which matches the answer.
'poor quality stuff is at start of auction' is the wordplay.
'poor quality stuff' becomes 'tat' (tat can mean low-quality items).
'is at start of' says to take the initial letters.
The first letter of 'auction' is 'a'.
'tat'+'a'='TA-TA'
Can you help me to learn more?
(Other definitions for ta-ta that I've seen before include "Adieu" , "Bye!" , "Cheerio" , "A Farewell" , "Bye-bye" .)