Thinks it’s a calculator (7)
I believe the answer is:
reckons
'thinks' is the definition.
(reckoning is a kind of thinking)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for reckons that I've seen before include "Considers" , "Calculates" , "Suspects" , "Estimates" , "Conkers (anag.)" .)