Quavering (9)
I believe the answer is:
tremulous
'quavering' is the definition.
(I know that quavering can be written as tremulous)
This is the entire clue.
(Other definitions for tremulous that I've seen before include "Shaky" , "Slightly shaking" , "Timid; shaking" , "Shaking, quivering" , "Timid; quivering" .)