leavening leaven

barm

appeal fillip impetus impulsion incitement stimulus whet

business commotion crisis dust-up fight fracas furor incident kerfuffle plate pother riot ruckus shindig stramash strife trouble

bobbery brouhaha fuss palaver roughhouse scrum tempest wild

beads bleb froth soap suds

bubble effervesce frothy

chance clue crowbar cue encouragement introduction lead occasion reason springboard timing tipping point turning point way