Pirate cap ordered according to population (3,6)

I believe the answer is:

per capita

I'm a little stuck... Click here to teach me more about this clue!

'according to population' is the definition.
I can't tell whether this defines the answer.

'pirate cap ordered' is the wordplay.
'ordered' is an anagram indicator.
'pirate'+'cap'='piratecap'
'piratecap' anagrammed gives 'PER CAPITA'.

Can you help me to learn more?

(Other definitions for per capita that I've seen before include "For each person - in routine Latin phrase" , "A head" , "apiece" .)

I've seen this clue in The Daily Express.

Want a hint initially instead of a full solution? Install my app