Lethargic entertainer taking part (5)
I believe the answer is:
inert
'lethargic' is the definition.
(synonyms)
'entertainer taking part' is the wordplay.
'part' says the answer is hidden in the clue.
'INERT' is hidden in the letters of 'entertainer taking'.
(Other definitions for inert that I've seen before include "lacking energy" , "Unable to move or resist motion" , "Slow and apathetic" , "Lifeless, sluggish" , "Passive, immobile" .)