Playground etiquette for calculator? (5,4)
I believe the answer is:
slide rule
'calculator?' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for slide rule that I've seen before include "old computer" , "Instrument for rapid calculations" , "Old calculator" , "Logs on here" , "facilitates calculations" .)