Back (7)
(Other definitions for endorse that I've seen before include "'Approve of, back (7)'" , "Say you approve" , "Uphold" , "Give public approval of (something)" , "Put one's name to, approve" .)
'back' is the definition.
(back can mean to reverse)
This is the entire clue.
(Other definitions for reverse that I've seen before include "Go backwards" , "Drive backwards" , "Britannia's place" , "Setback; go back" , "Severer (anag.)" .)
'back' is the definition.
(something's rear is its back)
This is all the clue.
(Other definitions for rear that I've seen before include "Bring up or stand up on hind legs" , "Of horse, rise up on hind legs" , "Raise; behind" , "Bring up - the tail" , "Back; bring up (young)" .)
'back' is the definition.
(both can mean to support an idea or proposal)
This is all the clue.
(Other definitions for second that I've seen before include "Assistant in the ring" , "Basic unit of time" , "Short period of time" , "Short space of time" , "Position of runner-up" .)
'back' is the definition.
('years back' means 'years ago')
This is the entire clue.
(Other definitions for ago that I've seen before include "Gone, past, since" , "Time past" , "Previously" , "(Years) before the present time" , "In past times" .)