Movement bound to be heard (4)
I believe the answer is:
tide
'movement' is the definition.
(I have seen 'Movement of seawater ' mean 'tide' so perhaps 'movement' could also mean 'tide')
'bound to be heard' is the wordplay.
'bound' becomes 'tied' (similar in meaning).
'to be heard' indicates a 'sounds like' (homophone) clue.
'tied' sounds like 'TIDE'.
(Other definitions for tide that I've seen before include "Ebber and flower?" , "Rising and falling of the sea" , "Movement of seawater" , "Regular movement" , "One thing that waits for no man" .)