You, long ago, housed in road that leads to government building (10)
I believe the answer is:
courthouse
'to government building' is the definition.
(I've seen this before)
'you long ago housed in road' is the wordplay.
'you long ago' becomes 'thou' (I've seen this in another clue).
'housed in' is an insertion indicator.
'road' becomes 'course' (I can't justify this - if you can you should give a lot more credence to this answer).
'thou' inserted into 'course' is 'COURTHOUSE'.
'that leads' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for courthouse that I've seen before include "where the action takes place" , "government building" , "suits here?" .)