Potter having a stint on Scottish island (4,5)
I believe the answer is:
muck about
'potter' is the definition.
(both can mean to fiddle with something)
'a stint on scottish island' is the wordplay.
'stint' becomes 'bout'.
'on' says to put letters next to each other.
'scottish island' becomes 'muck' (Muck is an island of the Small Isles).
'a'+'bout'='about'
'about' after 'muck' is 'MUCK ABOUT'.
'having' is the link.
(Other definitions for muck about that I've seen before include "Act in a silly way" , "Misbehave" , "Behave in a silly or aimless way" .)