Step up can be nasty when moving right to left (9)

I believe the answer is:

increment

I'm a little stuck... Click here to teach me more about this clue!

'step' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

(Other definitions for increment that I've seen before include "additional pay" , "Step" , "Rise" , "Small change" , "Addition to wages etc" .)

I've seen this clue in The Guardian.

Want a hint initially instead of a full solution? Install my app