Sleuth of inferior quality concealing hesitation (8)
I believe the answer is:
sherlock
'sleuth' is the definition.
(fictional detective Sherlock Holmes)
'of inferior quality concealing hesitation' is the wordplay.
'of inferior quality' becomes 'shlock' (shlock means cheap or shoddy).
'concealing' means one lot of letters goes inside another.
'hesitation' becomes 'er' (sound used when hesitating).
'shlock' placed around 'er' is 'SHERLOCK'.
(Other definitions for sherlock that I've seen before include "Fictional sleuth . . . . . . . . Holmes" , "detective - with 18a" , "Conan Doyle's sleuth, . . . . . . . . Holmes" , "Fictional detective" , "Arthur Conan Doyle's detective" .)