As venomous creatures presumably they don't multiply! (6)

I believe the answer is:

adders

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

'as venomous' is the definition.
'adders' can be an answer for 'venomous' (type of snake). I am unsure of the 'as' bit.

I can't explain the remainder of the clue.

Can you help me to learn more?

(Other definitions for adders that I've seen before include "Dreads (anag) -- snakes" , "People doing sums" , "Snakes are totters" , "Mathematical snakes" , "Poisonous snakes" .)

I've seen this clue in The Irish News.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.