Surge that's bound to be heard (4)
I believe the answer is:
tide
'surge' is the definition.
(I've seen this before)
'bound to be heard' is the wordplay.
'bound' becomes 'tied' (I've seen this before).
'to be heard' indicates a 'sounds like' (homophone) clue.
'tied' sounds like 'TIDE'.
'that's' is the link.
(Other definitions for tide that I've seen before include "(With time) it waits for no man" , "In the main, movement" , "Rising and falling of the sea" , "Periodic water movement" , "Periodic flow" .)