Remove permit to enter a Scottish river (6)
I believe the answer is:
delete
'remove' is the definition.
(I know that delete is a more specific form of the action remove)
'permit to enter a scottish river' is the wordplay.
'permit to' becomes 'let' (I've seen this before).
'enter' indicates putting letters inside.
'a scottish river' becomes 'dee' (I've seen this in another clue).
'let' going within 'dee' is 'DELETE'.
(Other definitions for delete that I've seen before include "Key" , "Erase or destroy" , "Eliminate" , "Eras" , "Rub out, expunge" .)