Dock where tide originally has King Canute unsettled (8)
I believe the answer is:
truncate
'dock' is the definition.
(I've seen this before)
'tide originally has king canute unsettled' is the wordplay.
'originally' indicates taking the first letters.
'has' says to put letters next to each other.
'king' becomes 'R' (abbreviation of Latin rex).
'unsettled' indicates an anagram.
The initial letter of 'tide' is 't'.
'canute' with letters rearranged gives 'uncate'.
't'+'r'+'uncate'='TRUNCATE'
'where' is the link.
(Other definitions for truncate that I've seen before include "Dock" , "Make shorter by cutting off" , "Shorten by cutting off the top" , "Cut short" , "Lop" .)