Mathematical process in class (8)
I believe the answer is:
division
I believe this clue is a double definition.
'mathematical process' is the first definition.
(division is a kind of mathematical process)
'class' is the second definition.
('division' can be a synonym of 'class')
'in' acts as a link.
(Other definitions for division that I've seen before include "some police?" , "Section; maths process" , "Group of football teams" , "Taking of a vote; partition" , "Large army unit" .)