Crack user with speed set aside (9)
I believe the answer is:
supersede
'set aside' is the definition.
(I've seen this before)
'crack user with speed' is the wordplay.
'crack' is an anagram indicator.
'with' is a charade indicator (letters next to each other).
'user'+'speed'='userspeed'
'userspeed' anagrammed gives 'SUPERSEDE'.
(Other definitions for supersede that I've seen before include "Take the place of, override" , "Supplant, replace" , "set aside" , "Take the place of, supplant" , "Stop using" .)