Millions in NZ city lacking land in a violent rage (5)
I believe the answer is:
amuck
'millions in nz city lacking land in a violent rage' is the definition.
I can't judge whether this definition defines the answer.
'in nz city lacking land in a violent rage' is the wordplay.
'in' is an insertion indicator.
'nz city' becomes 'auckland' (I've seen this before).
'lacking' suggests deleting specific letters.
'in a violent rage' becomes 'm' (I can't justify this - if you can you should give a lot more credence to this answer).
'auckland' with 'land' removed is 'auck'.
'auck' enclosing 'm' is 'AMUCK'.
Can you help me to learn more?
(Other definitions for amuck that I've seen before include "A mess gets one" , "In a frenzy" , "Behaving disruptively" , "Run this way to rush about violently and out of control" .)