Kind of wave; kind of bore (5)
I believe the answer is:
tidal
I believe this clue is a double definition.
'kind of wave' is the first definition.
(I've seen this in another clue)
'kind of bore' is the second definition.
(I've seen this in another clue)
(Other definitions for tidal that I've seen before include "going with the flow" , "(Waters) subject to moon/sun" , "Like waves" , "Concerning regular changes in sea level" , "Going back and forth" .)