Unstable, shaky (8)
I believe the answer is:
insecure
This clue is a double definition.
'unstable' is the first definition.
(thesaurus)
'shaky' is the second definition.
(similar in meaning)
(Other definitions for insecure that I've seen before include "open to attack" , "(Feeling) unsafe" , "Timid" , "Not adequately protected" , "Not firmly fixed" .)