Backward (6)
'backward' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for retrogressive that I've seen before include "Tending to return to an earlier state" , "Moving backwards" , "Showing backsliding" , "Going from better to worse" , "Going backwards" .)
'backward' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for astern that I've seen before include "The wake is" , "Abaft" , "Behind (naut.)" , "following behind vessel" , "Aft" .)