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

'a prisoner?' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.

'first person taken by northern clubs' is the wordplay.
'first person' becomes 'I' (first-person pronoun).
'taken by' means one lot of letters go next to another.
'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?