Crossword Genius

Mop up for the dog! (3)

Ross

I believe the answer is:

pom

Here is my best explanation:

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

'mop up' is the wordplay.
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'mop' in reverse letter order is 'POM'.

'for' acts as a link.

This clue was last seen in Evening Standard