Convinced pressure is on institute in Soviet organisation (8)
I believe the answer is:
positive
'convinced' is the definition.
('positive' can be a synonym of 'convinced')
'pressure is on institute in soviet organisation' is the wordplay.
'pressure' becomes 'p' (abbreviation).
'is on' is a charade indicator (letters next to each other).
'institute' becomes 'i' (common abbreviation as in MIT).
'in' is an insertion indicator.
'organisation' indicates an anagram.
'soviet' with letters rearranged gives 'ostive'.
'i' going into 'ostive' is 'ositive'.
'p'+'ositive'='POSITIVE'
(Other definitions for positive that I've seen before include "Definite, sure" , "Optimistic; certain" , "'Definite, categorical (8)'" , "Definite, confident" , "Constructive, optimistic" .)