The initial idioms of the letter A

sigh of relief	a sight
a sight for sore eyes	a sign of the times
significance level	a significant other
silk-stocking district	have a silver tongue
silver foil	a sin tax
a sine qua non	a sinking feeling
a sinking ship	siren song
a sitting duck	size queen
skeleton crew	skeleton in (the/one's) closet
a skeleton in the/ closet	a skeleton in the/ cupboard
skeleton in (the/one's) cupboard	skittles party
skunk at a garden party	a shouting match
a slap in the face	a slap on the back
a slap on the wrist	sledge-hammer argument
sleepy head	sleeveless errand