One taken by northern clubs as a prisoner? (2,5)

'a prisoner?' is the definition.
I know nothing about this answer so I cannot judge whether this works.

'one taken by northern clubs' is the wordplay.
'one' becomes 'i' (Roman numeral).
'taken by' says to put letters next to each other.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'clubs' becomes 'irons' (iron is a kind of club).
'i'+'n'+'irons'='IN IRONS'

'as' is the link.

Can you help me to learn more?