Utter lack of sparkle, possibly! (4)
I believe the answer is:
rasp
'utter' is the definition.
(rasping is a kind of uttering)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for rasp that I've seen before include "Grating noise; file" , "Coarse file or grating sound" , "Grate; scrape" , "Harsh grating sound" , "fruit" .)