idea
What a clever idea, I don't know why no one has thought of that before.
I'm always interested in hearing clever ideas about how we can improve our systems.
Trying to climb the cliff in a pair of flip-flops was not the cleverest idea.

SMART Vocabulary: related words and phrases

Intelligence
acuity
acumen
agility
apt
aptness
brain
gumption
highbrow
horse sense
hyper-intelligent
imaginative
perceptively
percipient
percipiently
perspicacious
perspicaciously
perspicacity
profundity
whip-smart
wisdom