Craft that's shipshape going to Inishmore, Inishmaan and Inisheer? (8)
I believe the answer is:
trimaran
'craft' is the definition.
(trimaran is a kind of craft)
'shipshape going to inishmore inishmaan and inisheer?' is the wordplay.
'shipshape' becomes 'trim' ('trim' can be a synonym of 'shipshape').
'going to' means one lot of letters go next to another.
'inishmore inishmaan and inisheer?' becomes 'aran' (aran islands).
'trim'+'aran'='TRIMARAN'
'that's' is the link.
(Other definitions for trimaran that I've seen before include "Three-hulled yacht" , "Three-hulled boat" , "Sailing boat with 3 hulls" , "Sailing vessel" , "Ocean vessel with three hulls side by side" .)