Clear, once one put speed on (9)
I believe the answer is:
exonerate
'clear' is the definition.
(to clear of criminal charges)
'once one put speed on' is the wordplay.
'once' becomes 'ex' (prefix meaning former or onetime).
'put' says to put letters next to each other.
'speed' becomes 'rate' (the speed at which something happens).
'on' is a charade indicator (letters next to each other).
'ex'+'one'+'rate'='EXONERATE'
(Other definitions for exonerate that I've seen before include "Clear of blame" , "Acquit" , "Declare to be blameless (9)" , "Discharge" , "Officially absolve from blame" .)