It jingles on a janitor's ring (3)
I believe the answer is:
key
(Other definitions for key that I've seen before include "explanation" , "Crucial; island" , "A major say" , "Device for lock" , "Vital" .)
I believe the answer is:
key
(Other definitions for key that I've seen before include "explanation" , "Crucial; island" , "A major say" , "Device for lock" , "Vital" .)