Put A Hill back on the list (4)
I believe the answer is:
rota
'the list' is the definition.
(rota is a kind of list)
'put a hill back' is the wordplay.
'put' becomes 'a' (I am not sure about this - if you are sure you should believe this answer much more).
'a hill' becomes 'tor' (tor is a kind of hill).
'back' says the letters should be written backwards.
'a'+'tor'='ator'
'ator' reversed gives 'ROTA'.
'on' acts as a link.
Can you help me to learn more?
(Other definitions for rota that I've seen before include "List of duties to be done, or people to do them" , "List of people to do job in turns" , "Ecclesiastical tribunal" , "Repetitious canon" , "Cycle of duty" .)