Departure from idea thrills (5)
I believe the answer is:
death
'departure' is the definition.
(I've seen this in another clue)
'from idea thrills' is the wordplay.
'from' says the answer is hidden in the clue.
'DEATH' is hidden in the letters of 'idea thrills'.
(Other definitions for death that I've seen before include "Last moment of existence" , "The end - after 13 across, the plague" , "Mortality" , "Cessation of life" , "Demise" .)