Volte-face by Caesar's killer leaving us and theatre in dismay (7)
I believe the answer is:
perturb
'dismay' is the definition.
(thesaurus)
'volte-face by caesar's killer leaving us and theatre' is the wordplay.
I cannot really see how this works, but
'by' could be 'per' and 'per' is located in the answer.
This explanation may well be incorrect...
'in' is the link.
Can you help me to learn more?
(Other definitions for perturb that I've seen before include "Disturb - trouble" , "Unsettle; PR brute (anag.)" , "Disquiet, disturb" , "Discountenance" , "Disconcert" .)