Made his Ben Hur intrinsically so long (5)
I believe the answer is:
adieu
'so long' is the definition.
(both can mean goodbye)
I don't understand how the remainder of the clue works.
(Other definitions for adieu that I've seen before include "Au revoir (to a kind friend?)" , "Farewell, adios" , "Farewel" , "Parting word" , "All the best" .)