Greek character leads small rebellion (6)
I believe the answer is:
mutiny
'rebellion' is the definition.
(mutiny is a kind of rebellion)
'greek character leads small' is the wordplay.
'greek character' becomes 'mu' (letter from the Greek alphabet).
'leads' means one lot of letters go next to another.
'small' becomes 'tiny' ('tiny' can be similar in meaning to 'small'**).
'mu'+'tiny'='MUTINY'
(Other definitions for mutiny that I've seen before include "Military rebellion" , "Open rebellion against constituted authority" , "Rising, rebellion" , "Rebellion as on Bligh's Bounty" , "Rebellion in the armed forces" .)