Hideout Scottish landowner left unfinished (4)
I believe the answer is:
lair
'hideout' is the definition.
(thesaurus)
'scottish landowner left unfinished' is the wordplay.
'scottish landowner' becomes 'laird' (I've seen this before).
'left unfinished' means to remove the last letter.
'laird' with its last letter taken off is 'LAIR'.
(Other definitions for lair that I've seen before include "Rail about wild animal's home" , "animal refuge" , "Rail around hiding-place" , "Earth" , "Animal's resting place" .)