Do they deal with tots at the zoo? (6)
I believe the answer is:
adders
This clue is a double definition.
'do they deal with tots' is the first definition.
(I've seen this before)
'at the zoo?' is the second definition.
(I've seen this before)
(Other definitions for adders that I've seen before include "at the zoo?" , "Mathematical snakes" , "Arithmetic snakes?" , "Small vipers" , "sum? We do" .)