It rises and falls and it returns half dead (4)
I believe the answer is:
tide
'it rises and falls' is the definition.
(I've seen this in another clue)
'it returns half dead' is the wordplay.
'returns' says the letters should be written backwards.
'half' indicates taking half.
'it' written backwards gives 'ti'.
'dead' halved is 'de'.
'ti'+'de'='TIDE'
'and' is the link.
(Other definitions for tide that I've seen before include "turning point" , "Ebb and flow of the sea" , "Season; current" , "Movement of seawater" , "Periodic flow" .)