State of hair in dogs outside bars? (9)

'state of hair' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.

'dogs outside bars?' is the wordplay.
'dogs' becomes 'curs' (cur can mean a violent dog).
'outside' means one lot of letters goes inside another (some letters go outside others).
'bars?' becomes 'lines' (bar can mean a line).
'curs' placed around 'lines' is 'CURLINESS'.

'in' is the link.

Can you help me to learn more?