NB: it's just been delivered (7)
I believe the answer is:
newborn
'nb it's' is the definition.
I can't tell whether this defines the answer.
'been delivered' is the wordplay.
'been' becomes 'new' (I am not sure about this - if you are sure you should believe this answer much more).
'delivered' becomes 'born' (as in a baby being delivered).
'new'+'born'='NEWBORN'
'just' is the link.
Can you help me to learn more?
(Other definitions for newborn that I've seen before include "Neonate" , "Recently given birth to" , "Young baby" , "Recently delivered" , "Just entered the world" .)