Come forward with an increment (4,2)

I believe the answer is:

step up

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

'come forward' is the definition.
(synonyms)

I cannot understand how the rest of the clue works.

(Other definitions for step up that I've seen before include "Approach" , "Advancement (on a ladder or career)" , "Increase as with pace - or ascend stair?" , "Raise by stages" , "To be promoted" .)

I've seen this clue in the Evening Standard.

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