Implied MP switching to Liberal is unlawful (7)
I believe the answer is:
illicit
'is unlawful' is the definition.
(similar in meaning)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for illicit that I've seen before include "breaking the law" , "Not approved by law" , "Without approval" , "Felonious" , "completely banned" .)