The initial idioms of the letter A

a waste of breath	a waste of energy
a watched kettle never boils	A watched pot never boils
a way of life	a weak link
weaker vessel	weather breeder
wedding cake	a week from next Tuesday
a week is a long time in politics	weight off (one's) mind
welfare Cadillac	a wet blanket
a wet dream	mad as a hornet
a whale of a	a whale of a [bill etc.]
a whale of a [job etc.]	a whale of a (good) time
wheel within a wheel	a while back
a whipping boy	a whip-round
a whistle-stop tour	a white elephant
a white knight	a white lie
white man	white marriage