Pressure, say, gutted a revolutionary spirit (6)
I believe the answer is:
psyche
'spirit' is the definition.
(psyche can mean spirit or soul)
'pressure say gutted a revolutionary' is the wordplay.
'pressure' becomes 'p' (abbreviation).
'gutted' says to hollow out the word (remove centre letters) (to gut something is to remove its insides).
'a revolutionary' becomes 'che' (Che Guevara the Marxist revolutionary).
'say' with its centre removed is 'sy'.
'p'+'sy'+'che'='PSYCHE'
(Other definitions for psyche that I've seen before include "Inner self" , "Soul, spirit; lover of Cupid" , "Soul; Cupid loved her" , "The soul, spirit or mind" , "Human faculty for thought - Cupid's lover" .)