Back (7)
'back' is the definition.
(back can mean to reverse)
This is the entire clue.
(Other definitions for reverse that I've seen before include "Rescind (decision)" , "Upset" , "Transpose" , "Britannia's place" , "One side of a coin" .)
'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 - the tail" , "Back; bring up (young)" , "what can be brought up, finally" , "Bring up and care for" , "Stern" .)
'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 "not for long!" , "Short time; attendant at a duel" , "Back-up; short time" , "Not first team (6,6) - See 25" , "Mo" .)
'back' is the definition.
('years back' means 'years ago')
This is the entire clue.
(Other definitions for ago that I've seen before include "Previously" , "In past times" , "(Years) before the present time" , "Earlier, gone by" , "Gone, past, since" .)