Complain about foreigners essentially occupying a Scottish island (7)
I believe the answer is:
arraign
'complain about' is the definition.
(I've seen this before)
'foreigners essentially occupying a scottish island' is the wordplay.
'essentially' means to look at the middle letters.
'occupying' is an insertion indicator.
'a scottish island' becomes 'arran' (I've seen this before).
The central letters of 'foreigners' are 'ig'.
'ig' put into 'arran' is 'ARRAIGN'.
(Other definitions for arraign that I've seen before include "Indict, accuse" , "Call to account" , "Accuse before tribunal" , "Accuse publicly" , "Call before court to answer criminal charge" .)