I'm not sure about small-scale rebellion (6)
I believe the answer is:
mutiny
'rebellion' is the definition.
(I know that mutiny is a type of rebellion)
'i'm not sure about small-scale' is the wordplay.
'i'm not sure' becomes 'um' (expression of hesitation).
'about' shows that the letters should be reversed in order.
'small-scale' becomes 'tiny'.
'um' back-to-front is 'mu'.
'mu'+'tiny'='MUTINY'
(Other definitions for mutiny that I've seen before include "Rebellion in the armed forces" , "Rising, rebellion" , "Revolt against authority" , "Open rebellion against constituted authority" , "Open rebellion by sailors or soldiers" .)