Nothing new purchased, having missed opening (6)
I believe the answer is:
nought
'nothing' is the definition.
(synonyms)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for nought that I've seen before include "The figure 0" , "Go hunt for nothing" , "The digit 0" , "duck" , "Poetically nothing" .)