Note quiet enveloping North Island's lowest point (7)
I believe the answer is:
minimum
'lowest point' is the definition.
(I've seen this before)
'note quiet enveloping north island's' is the wordplay.
'note' becomes 'mi' (as in 'do re mi').
'quiet' becomes 'mum' (I've seen this before).
'enveloping' indicates putting letters inside.
'north island' becomes 'ni' (this could be a standard abbreviation of which I'm unaware).
'mi'+'mum'='mimum'
'mimum' placed around 'ni' is 'MINIMUM'.
Can you help me to learn more?
(Other definitions for minimum that I've seen before include "Bottom" , "Lowest value" , "The least of smallest amount possible" , "Lowest point" , "Smallest possible quantity" .)