No good to perform in Kim’s realm (7)
I believe the answer is:
kingdom
'realm' is the definition.
(I know that realm can be written as kingdom)
'no good to perform in kim's' is the wordplay.
'no good' becomes 'ng' (abbreviation).
'to perform' becomes 'do' (both can mean complete an action).
'in' indicates putting letters inside.
'ng'+'do'='ngdo'
'ngdo' inserted into 'kim' is 'KINGDOM'.
(Other definitions for kingdom that I've seen before include "State ruled by monarch" , "State with a monarchy" , "Republic? Not so!" , "Country with royal head of state" , "Major category of biological classification" .)