Worn out, occasionally unsteady (4)
I believe the answer is:
used
'worn out' is the definition.
'used' can be an answer for 'worn' (I've seen this in another clue). I'm not sure about the 'out' bit.
'occasionally unsteady' is the wordplay.
'occasionally' means one should take alternating letters.
The alternate letters of 'unsteady' are 'USED'.
Can you help me to learn more?
(Other definitions for used that I've seen before include "Employed in task, or second-hand" , "no stranger" , "Availed oneself of" , "Second-hand - not wasted" , "Exploited group" .)