Bill firm millions, and the Law loses love for partner in crime (10)
I believe the answer is:
accomplice
'for partner in crime' is the definition.
(I've seen this before)
'bill firm millions' is the wordplay.
'bill' becomes 'ac'.
'firm millions' becomes 'complice' (I can't justify this - if you can you should give a lot more credence to this answer).
'ac'+'complice'='ACCOMPLICE'
'and the law loses love' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for accomplice that I've seen before include "Partner in crime" , "Colleague" , "Criminal's associate" , "Fellow criminal" , "Partner in plan" .)