He was bound to prove entertaining (7)
I believe the answer is:
houdini
'he was bound' is the definition.
(Harry Houdini was frequently tied up or bound)
I can't explain the rest of the clue.
(Other definitions for houdini that I've seen before include "Harry . . . . . . ., famed American escapologist" , "Expert at escaping" , "being given to escapism?" , "one who'd try to escape?" , "Escape artist, d. 1926" .)