Criminal author will grab a stick to boomerang (7)
I believe the answer is:
illegal
'criminal' is the definition.
(similar in meaning)
'author will grab a stick to boomerang' is the wordplay.
I cannot quite see how this works, but
'will' could be 'll' (contracted form, as in 'he'll' - 'he will') and 'll' is present in the answer.
'a' is within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for illegal that I've seen before include "Unlawful" , "Such an immigrant" , "Black-market" , "Contraband" , "Wrong" .)