Solution to The Wheels Go Round and Round

Solution to the clues:

CH₂O solution used as a preservative	FORMALIN
“Northern” fish	PIKE
“Psst!”	LISTEN
Slippery to the max	EELIEST
Twenty-third of twenty-four	PSI
Valse ou rigaudon	DANSE

Barely wet one’s whistle	SIP
Gendarme’s ceremonial cap	KEPI
Metallic playing marble	STEELIE
Not burdened by stiff ceremony	INFORMAL
Sign on	ENLIST

Each word in the top, except for DANSE, can be tranformed to get a word on the bottom by moving two letters from the end to the beginning. (For example, FORMALIN becomes INFORMAL.) If we apply this transformation to the leftover word DANSE, we get SEDAN, which is the answer.

Solution to The Wheels Go Round and Round

by Noam D. Elkies