The initial idioms of the letter A

low profile	assume liability for
assume the mantle	assume the position
labor under an assumption	assure
assure (one) of	assure of
back-assward	ass-wipe
be nothing short of [astonishing etc.]	Mrs. Astor's plush horse
astound	astound (one) with
astound with	astray
keep astride of (something)	asylum
at (long) last	at (one's) best
at (one's) earliest convenience	at (one's) ease
at (one's) elbow	at (one's) expense
at (one's) fingertips	at (one's) heels
at (one's) knee	at (one's) leisure
at (one's) mother's knee	at (one's) own game