A summer snake? (5)

I believe the answer is:

adder

I believe this clue is a double definition.

'a summer' is the first definition.
(someone who adds or does sums)

'snake' is the second definition.
(type of snake)

(Other definitions for adder that I've seen before include "Poisonous Brit. snake" , "Type of snake" , "Totter" , "Dread (anag)" , "venomous creature" .)

I've seen this clue in The Irish News and The Globe and Mail.

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