Crossword Genius

Reprimands where blood-suckers should be? (5,3)

Ross

I believe the answer is:

ticks off

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

'reprimands' is the definition.
Although both the answer and definition are verbs in their -s form, I don't understand how they can define each other.

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for ticks off that I've seen before include "Checks - upbraids" , "may be seconds away" , "Carpets" .)

I've seen this clue in the Sydney Morning Herald.
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