Old and unsteady, occasionally (4)
I believe the answer is:
used
'old' is the definition.
(as in used or second-hand items)
'unsteady occasionally' is the wordplay.
'occasionally' indicates alternate letters (letters taken at regular intervals or occasions).
The alternate letters of 'unsteady' are 'USED'.
'and' is the link.
(Other definitions for used that I've seen before include "Previously owned by another" , "with some traffic" , "Dues (anag.)" , "Sued (anag.)" , "Utilised" .)