Consider or calculate (6)
I believe the answer is:
reckon
I believe this clue is a double definition.
'consider' is the first definition.
(I know that consider is a more specific form of the action consider)
'calculate' is the second definition.
(I know that calculate can be written as reckon)
(Other definitions for reckon that I've seen before include "Count or calculate" , "Conker (anag.)" , "Calculate, be of the opinion" , "Suppose or calculate" , "Consider, judge to be probable" .)