x, for one
I believe the answer is:
axis
'x for one' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for axis that I've seen before include "Spindle - German/Italian alliance - deer" , "Centre about which something turns" , "Imaginary line about which a body rotates and a Dublin theatre" , "WW2 Nazi alliance" , "World War two Italy-Germany alliance" .)