Unstable leader back in charge worried tyke (7)
I believe the answer is:
rickety
'unstable' is the definition.
(similar in meaning)
'leader back in charge worried tyke' is the wordplay.
'back' says to take the final letters (the letter at the back).
'in charge' becomes 'ic' (abbreviation for 'in charge').
'worried' indicates anagramming the letters (worry can mean to interfere with or disturb).
The final letter of 'leader' is 'r'.
'tyke' with letters rearranged gives 'kety'.
'r'+'ic'+'kety'='RICKETY'
(Other definitions for rickety that I've seen before include "Shaky" , "liable to collapse" , "Unsteady" , "Not built to last" , "Likely to collapse" .)