Places echo after shell goes off in coup (6)
I believe the answer is:
putsch
'coup' is the definition.
(synonyms)
'places echo after shell goes off' is the wordplay.
'places' becomes 'puts' ('put' can be a synonym of 'place').
'after shell goes off' indicates the central letters (the shell or case of the word is removed).
The centre of 'echo' is 'ch'.
'puts'+'ch'='PUTSCH'
'in' acts as a link.
(Other definitions for putsch that I've seen before include "A sudden political uprising" , "political revolt" , "rising" , "A sudden political rebellion" , "Sudden illegal acquisition of power" .)