Most of panel on a Hebridean island (4)
I believe the answer is:
jura
'hebridean island' is the definition.
(I've seen this before)
'most of panel on a' is the wordplay.
'most of' means to remove the last letter.
'panel' becomes 'jury' ('jury' can be a synonym of 'panel').
'on' means one lot of letters go next to another.
'jury' with its final letter removed is 'jur'.
'jur'+'a'='JURA'
(Other definitions for jura that I've seen before include "Inner Hebrides isle" , "island > range" , "European mountain range" , "Inner Hebrides island" , "Scottish island -- mountains on the French-Swiss border" .)