WordNet sense 1 (having keenness and forcefulness and penetration in thought, expression, or intellect):

searching

WordNet sense 2 (having the capacity for thought and reason especially to a high degree):

intelligent

WordNet sense 3 (characterized by or full of force and vigor):

hard-hitting

WordNet sense 4 (producing or capable of producing an intended result or having a striking effect):

effective, effectual, efficacious

WordNet sense 5 (clearly or sharply defined to the mind):

clear-cut, distinct

WordNet sense 6 (clear to the mind):

clear