Old joke to admire is clear (9)
I believe the answer is:
exonerate
'is clear' is the definition.
(to clear of criminal charges)
'old joke to admire' is the wordplay.
'old' becomes 'ex' (prefix meaning former or onetime).
'joke' becomes 'one' (as in 'that's a good one!').
'to admire' becomes 'rate' (I've seen this before).
'ex'+'one'+'rate'='EXONERATE'
(Other definitions for exonerate that I've seen before include "Clear of blame" , "Free of duty" , "Discharge" , "let off the hook" , "Declare to be free from blame" .)