Redding who wrote "Respect" (4)
I believe the answer is:
'redding who wrote respect' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for otis that I've seen before include "Miss -- Regrets, Cole Porter song" , "Company providing lifts" , "Regretful miss" , "US inventor" , "Cole Porter's miss who was "unable to lunch today"" .)