Sphinx Riddle From Harry Potter And The Goblet Of Fire

Riddle: "First think of the person who lives in disguise, Who deals in secrets and tells naught but lies. Next, tell me what's always the last thing to mend, The middle of the middle and end of the end? And finally, give me the sound often heard During the search for a hard-to-find word. Now string them together, and answer me this, Which creature would you be unwilling to kiss?"