Furtively

1 clue
On the sly
Similar answers:
Abrasively
Abusively
Actively
Alternatively
Attentively
Blakelively
Coercively
Cohesively
Comprehensively
Consecutively
Consecutivelyin
Constructively
Deceptively
Decisively
Defensively
Demonstratively
Derisively
Effectively
Evasively
Excessively