Scottish island’s current proprietor mentioned in speech (4)
I believe the answer is:
iona
'scottish island's' is the definition.
(island of the Hebrides)
'current proprietor mentioned in speech' is the wordplay.
'current' becomes 'I' (symbol for electric current).
'proprietor' becomes 'owner' (synonyms).
'mentioned in speech' shows a homophone (sound like).
'owner' is a homophone of 'ona'.
'i'+'ona'='IONA'
(Other definitions for iona that I've seen before include "place in the Hebrides" , "Hebridean location" , "St Columba's monastery isle" , "Scots monastery isle" , "Scottish island noted for St Columba" .)