Detailed what speed Dennis regularly goes over (2-5)
I believe the answer is:
in-depth
'detailed' is the definition.
(I've seen this before)
'what speed dennis regularly goes over' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'goes over' shows that the letters should be reversed in order.
'what'+'speed'+'dennis'='whatspeeddennis'
The alternate letters of 'whatspeeddennis' are 'htpedni'.
'htpedni' written backwards gives 'IN-DEPTH'.
(Other definitions for in-depth that I've seen before include "Getting to the bottom of it" , "Thorough and intensive" , "Comprehensive and thorough" , "searching" , "Profoundly (studied)" .)