Shrewd
Part of speech: adjective
Definition: showing clever resourcefulness in practical matters artful, tricky or cunning streetwise
Example sentence: They made a shrewd guess that I could give them some useful information, and they were the first to meet me. Some one said they came to arrest me, and - well, let it go at that.
Conniving
Part of speech: verb
Definition: Often followed by with: to secretly cooperate with another person or persons in order to commit a crime or other wrongdoing; to collude, to conspire.
Part of speech: adjective
Definition: That connives; conspiratorial