Upright character recalled writing practice (3)
I believe the answer is:
ism
'practice' is the definition.
(I've seen this in another clue)
'upright character recalled writing' is the wordplay.
'upright character' becomes 'I' (vertical letter of the alphabet).
'recalled' says the letters should be written backwards (to recall can mean to bring something back).
'writing' becomes 'MS' (abbreviation for manuscript).
'ms' backwards is 'sm'.
'i'+'sm'='ISM'
(Other definitions for ism that I've seen before include "Informal doctrine found in Bismarck" , "Any branch of philosophy" , "Any system of beliefs" , "Informal noun or suffix for doctrine or practice" , "Suffix denoting doctrine or practice" .)