Seeing dagger in Caesar's back twisted (9)
I believe the answer is:
regarding
'seeing' is the definition.
('regard' can be a synonym of 'see')
'dagger in caesar's back twisted' is the wordplay.
'back' suggests the final letters.
'twisted' indicates an anagram.
The last letter of 'caesar' is 'r'.
'dagger'+'in'+'r'='daggerinr'
'daggerinr' with letters rearranged gives 'REGARDING'.
(Other definitions for regarding that I've seen before include "Considering" , "With respect to" , "Thinking" , "Concerned with" , "Seeing" .)