A vegetable – and it gets consumed with alacrity (8)
I believe the answer is:
celerity
'alacrity' is the definition.
(thesaurus)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for celerity that I've seen before include "Haste" , "Pace" , "Rapidity, speediness" , "Quickness" , "Dispatch" .)