Speed confused with speed - hopeless (9)
I believe the answer is:
desperate
'hopeless' is the definition.
(similar in meaning)
'speed confused with speed' is the wordplay.
'confused' indicates anagramming the letters.
'with' means one lot of letters go next to another.
'speed' becomes 'rate' (the speed at which something happens).
'speed' is an anagram of 'despe'.
'despe'+'rate'='DESPERATE'
(Other definitions for desperate that I've seen before include "Eater sped to beyond hope" , "Without hope" , "Feeling hopeless" , "Miserable" , "Having lost all hope" .)