It is an adjective.
Meaning : often planning secretly to do something for your own advantage, especially by deceiving other people. It indicates the cunning nature of a person.
Synonyms : cunning crafty, calculating, devious, designing, conniving, wily, sly, tricky, artful, guileful
schemingly - adverb
1)She was too gullible and unsuspecting to understand his scheming nature.
2)One has to be careful while dealing with scheming persons.
3)He is worried about his position as he got hooked up in the scheming plan made by the rival against his boss.
4)His scheming attitude had resulted him to this degraded position.