Doddery duke missing from Beds town (8)
I believe the answer is:
unstable
'doddery' is the definition.
(doddery can mean unstable or wobbly)
'duke missing from beds town' is the wordplay.
'duke' becomes 'd' (abbreviation).
'missing from' suggests deleting specific letters.
'beds town' becomes 'Dunstable' (town in Bedfordshire).
'dunstable' with 'd' taken out is 'UNSTABLE'.
(Other definitions for unstable that I've seen before include "not settled" , "Subject to change, variable" , "Wobbly" , "Prone to mood swings" , "lacking security" .)