Released, being old and almost completely useless (6)
I believe the answer is:
exempt
'released' is the definition.
(I've seen this in another clue)
'being old and almost completely useless' is the wordplay.
I cannot really see how this works, but
'being' could be 'mp' (MP is an example) and 'mp' is found in the answer.
'old' could be 'ex' (prefix meaning former or onetime) and 'ex' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for exempt that I've seen before include "Free (from taxes, etc)" , "Not subject to (eg taxation)" , "not expected to pay" , "Absolved" , "Not liable, as others may be" .)