Rise and fall of the sea temperature above fish (4)
I believe the answer is:
tide
'rise and fall of the sea' is the definition.
(the tide rises and falls)
'temperature above fish' is the wordplay.
'temperature' becomes 't' (abbreviation).
'above' says to put letters next to each other.
'fish' becomes 'ide' (type of fish).
't'+'ide'='TIDE'
(Other definitions for tide that I've seen before include "Surge of events" , "Ebber and flower?" , "Periodic rise and fall of the sea" , "''There is a ... in the affairs of men'' (Julius Caesar)" , "Ebb and flow of the sea" .)