Beginning to scare me, describing revolutionary's plot (6)
I believe the answer is:
scheme
'plot' is the definition.
(I know that scheme is a type of plot)
'beginning to scare me describing revolutionary's' is the wordplay.
'beginning to' indicates taking the first letters.
'describing' indicates putting letters inside (describe can mean to form the outline of).
'revolutionary' becomes 'che' (Che Guevara the Marxist revolutionary).
The initial letter of 'scare' is 's'.
's'+'me'='sme'
'sme' placed around 'che' is 'SCHEME'.
(Other definitions for scheme that I've seen before include "Plan, ruse" , "Plot, plan secretly" , "Elaborate and systematic plan of action" , "System or strategy" , "Hatch - plot" .)