Remarkable bar next to Hebridean island lake (11)
I believe the answer is:
exceptional
'remarkable' is the definition.
(thesaurus)
'bar next to hebridean island lake' is the wordplay.
'bar' becomes 'except' (both can mean 'not including').
'next to' means one lot of letters go next to another.
'hebridean island' becomes 'iona' (island of the Hebrides).
'lake' becomes 'L' (geographical abbreviation).
'except'+'iona'+'l'='EXCEPTIONAL'
(Other definitions for exceptional that I've seen before include "Outstanding; not typical" , "Extraordinary!" , "Unusually good" , "Very unusual" , "Out of the ordinary" .)