For example, x and y across primarily, the other going vertically? (4)
I believe the answer is:
axes
'for example x and y' is the definition.
'across primarily the other going vertically?' is the wordplay.
'primarily' suggests taking the first letters.
'the other' becomes 'sex' (old-fashioned slang term).
'going vertically?' is a reversal indicator.
The first letter of 'across' is 'a'.
'sex' in reverse letter order is 'xes'.
'a'+'xes'='AXES'
(Other definitions for axes that I've seen before include "Terminates" , "Dispenses with" , "X, Y scales on graph" , "equipment for lumberjack" , "lines at fourteen's [RIGHT ANGLES]" .)