cinch

(noun) any undertaking that is easy to do. Synonyms: breeze, picnic, snap, duck soup, child's play, pushover, walkover, piece of cake. Example: "Marketing this product will be no picnic."

(noun) stable gear consisting of a band around a horse's belly that holds the saddle in place. Synonyms: girth.

(noun) a form of all fours in which the players bid for the privilege of naming trumps.

(verb) tie a cinch around. Synonyms: girth. Example: "Cinch horses."

(verb) make sure of.

(verb) get a grip on; get mastery of.