Take out permit to enter Scottish river (6)
I believe the answer is:
delete
'take out' is the definition.
(deleting is a kind of taking out)
'permit to enter scottish river' is the wordplay.
'permit to' becomes 'let' (I've seen this before).
'enter' means one lot of letters goes inside another.
'scottish river' becomes 'dee' (I've seen this before).
'let' placed inside 'dee' is 'DELETE'.
(Other definitions for delete that I've seen before include "'Cancel, cut (6)'" , "Strike out (text)" , "Eras" , "Cancel, erase" , "Remove or erase (text)" .)