Boat to dock beside Irish islands (8)
I believe the answer is:
trimaran
'boat' is the definition.
(trimaran is a kind of sailing vessel)
'dock beside irish islands' is the wordplay.
'dock' becomes 'trim' (I am not sure about this - if you are sure you should believe this answer much more).
'beside' is a charade indicator (letters next to each other) (I've seen this in other clues).
'irish islands' becomes 'aran' (I've seen this before).
'trim'+'aran'='TRIMARAN'
'to' is the link.
Can you help me to learn more?
(Other definitions for trimaran that I've seen before include "Sailing vessel" , "Three-hulled boat" , "Three-hulled craft" , "Sailing boat with three hulls" , "Ocean vessel with three hulls side by side" .)