Clue: Fifth in Crufts, I'm amazed obedient dog moped, say (3-7)
Answer: TWO-WHEELER
Explanation: Definition: moped, say
 **5th letter of**(Fifth in) "Crufts" + WOW!(an expression of amazement/I'm amazed!) + HEELER(one, usually an obedient dog, that responds to the command, "Heel!").
Defn: An example of which/say, is the moped.
And Crufts, of course, is the largest dog show.