Small-scale revolt ousting character in Athens (4)
I believe the answer is:
tiny
'small-scale' is the definition.
'revolt ousting character in athens' is the wordplay.
'revolt' becomes 'mutiny' (mutiny is a kind of revolt).
'ousting' suggests deleting specific letters.
'character in athens' becomes 'mu' (Greek letter).
'mutiny' with 'mu' taken away is 'TINY'.
(Other definitions for tiny that I've seen before include "Quite insignificant" , "Little" , "Wee" , "Really small" , "Extremely small" .)