Creature never nonplussed? (5)

I believe the answer is:

adder

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'creature' is the definition.
(I have seen 'venomous creature' mean 'adder' so perhaps 'creature' could also mean 'adder')

I can't explain the rest of the clue.

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(Other definitions for adder that I've seen before include "Reptilian" , "Venemous snake" , "1 of 21 [SNAKES]" , "danger in the countryside" , "Totting snake" .)

I've seen this clue in the Evening Standard.

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