Harbour stops giving signals (8)
I believe the answer is:
portends
'signals' is the definition.
(portending is a kind of signaling)
'harbour stops' is the wordplay.
'harbour' becomes 'port' (I've seen this before).
'stops' becomes 'ends' ('end' can be a synonym of 'stop').
'port'+'ends'='PORTENDS'
'giving' is the link.
(Other definitions for portends that I've seen before include "Gives warning" , "Augurs, bodes" , "Signals" , "Warns" , "Indicates by signs" .)