Cast admitting exhausted ensemble is a sensation (7)
I believe the answer is:
feeling
'sensation' is the definition.
(I know that feeling is a sensation)
'cast admitting exhausted ensemble' is the wordplay.
'cast' becomes 'fling' (both can mean to throw).
'admitting' indicates putting letters inside (admit can mean to welcome in or accept).
'exhausted' means to remove the middle letters (the word is emptied out or exhausted).
'ensemble' with its middle taken out is 'ee'.
'fling' going around 'ee' is 'FEELING'.
'is a' is the link.
(Other definitions for feeling that I've seen before include "Sensation" , "Sense, emotion" , "Emotion; opinion" , "Sympathy" .)