Before entrance, Liberal on and on about Democrat's old authority (6,9)

'on about democrat's old authority' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.

'before entrance liberal on' is the wordplay.
'before' means one lot of letters go next to another.
'entrance' becomes 'transport' (I've seen this before).
'liberal on' becomes 'london' (I can't justify this - if you can you should believe this answer much more).
'transport' put after 'london' is 'LONDON TRANSPORT'.

'and' is the link.

Can you help me to learn more?