A jail made of pine bark (4,3)

I believe the answer is:

long bay

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

'a jail made' is the definition.
I know nothing about this answer so I can't tell whether this works.

'pine bark' is the wordplay.
'pine' becomes 'long' (synonyms).
'bark' becomes 'bay' (baying is a kind of barking).
'long'+'bay'='LONG BAY'

'of' acts as a link.

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.

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