Adder and when you’ll see one most often? (6)
I believe the answer is:
summer
'adder' is the definition.
(someone adding up or doing sums)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for summer that I've seen before include "Beam" , "'Oh, the ...time is comin', and the leaves are sweetly bloomin'' (song)" , "Late singer" , "Adder" , "'. . . . . . time an' the livin' is easy' (song)" .)