Rebellion by sailors or soldiers (6)
I believe the answer is:
mutiny
'rebellion by sailors or soldiers' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for mutiny that I've seen before include "Rebellion as on Bligh's Bounty" , "Rebellion in the armed forces" , "Insurrection" , "Open rebellion against constituted authority" , "Military rebellion" .)