Demands payment in accordance with obsolete laws (6)
I believe the answer is:
exacts
'demands payment in accordance' is the definition.
'exacts' can be an answer for 'demands' ('exact' can be a synonym of 'demand'). I am unsure of the 'payment in accordance' bit.
'obsolete laws' is the wordplay.
'obsolete' becomes 'ex' (I can't explain this - if you can you should believe this answer much more).
'laws' becomes 'acts' (I've seen this before).
'ex'+'acts'='EXACTS'
'with' acts as a link.
Can you help me to learn more?
(Other definitions for exacts that I've seen before include "Compels to furnish" , "making demands" , "Extorts" , "Compels payment of" , "Insists on or claims" .)