Independent check kept by socialist, fascinated (7)
I believe the answer is:
riveted
'fascinated' is the definition.
(I've seen this before)
'independent check kept by socialist' is the wordplay.
'independent' becomes 'i'.
'check' becomes 'vet' (to vet someone is to check their background).
'kept by' is an insertion indicator.
'socialist' becomes 'red' (socialism is often associated with the colour red).
'i'+'vet'='ivet'
'ivet' going within 'red' is 'RIVETED'.
(Other definitions for riveted that I've seen before include "Held firmly" , "Immovably fixed" , "Fixed (as attention may be)" , "Rooted to the spot with metal pins" , "Rendered motionless by concentration" .)