Significant symbol, trimmed at edges, encapsulating a city after revolution (9)
I believe the answer is:
memorable
'significant' is the definition.
(thesaurus)
'symbol trimmed at edges encapsulating a city after revolution' is the wordplay.
'symbol' becomes 'emblem' (emblem is a kind of symbol).
'trimmed at edges' indicates the central letters.
'encapsulating' means one lot of letters goes inside another (I've seen this in other clues).
'city' becomes 'rome' (Rome is an example**).
'after revolution' says the letters should be written in reverse.
The middle of 'emblem' is 'mble'.
'a'+'rome'='arome'
'arome' back-to-front is 'emora'.
'mble' enclosing 'emora' is 'MEMORABLE'.
(Other definitions for memorable that I've seen before include "Easily recalled" , "Catchy" , "Special" , "noteworthy" .)