Listless diner tasted ingredients (5)
I believe the answer is:
inert
'listless' is the definition.
(I've seen this in another clue)
'diner tasted ingredients' is the wordplay.
'ingredients' indicates a hidden word (certain parts or ingredients from the clue).
'INERT' is hidden in the letters of 'diner tasted'.
(Other definitions for inert that I've seen before include "Torpid" , "Unreactive; still" , "Like e.g. xenon" , "Without the strength to move" , "Sluggish, inactive" .)