One in alliance with extremely nervous groups of people (7)

'groups of people' is the definition.
The definition and answer can be both groups as well as being plural nouns.
Maybe you can see a link between them that I can't see?

'one in alliance with extremely nervous' is the wordplay.
'one' becomes 'I' (Roman numeral).
'in' indicates putting letters inside.
'alliance' becomes 'nato' (NATO is an example).
'with' means one lot of letters go next to another.
'extremely' means to remove the middle letters (only the extremes of the word are used).
'nervous' with its middle taken out is 'ns'.
'i' going into 'nato' is 'natio'.
'natio'+'ns'='NATIONS'

Can you help me to learn more?