Think what people who count will do (6)
I believe the answer is:
reckon
I believe this clue is a double definition.
'think' is the first definition.
(I know that think can be written as reckon)
'what people who count will do' is the second definition.
(I've seen this before)
(Other definitions for reckon that I've seen before include "Consider, judge to be probable" , "Believe, suppose, judge" , "Have as opinion or count up" , "Consicer or calculate" , "Consider or calculate" .)