Of the rise and fall of the sea (5)
I believe the answer is:
tidal
'of the rise and fall of the sea' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for tidal that I've seen before include "Relating to the rise and fall of the sea" , "Concerning the rise and fall of the sea" , "Subject to ebb and flow" , "subject to regular surges" , "(Waters) subject to moon/sun" .)