Landowner's day off in retreat (4)
I believe the answer is:
lair
'retreat' is the definition.
(thesaurus)
'landowner's day off' is the wordplay.
'landowner' becomes 'laird' (Scottish term for a landowner).
'day' becomes 'd'.
'off' suggests deleting specific letters.
'laird' with 'd' removed is 'LAIR'.
'in' is the link.
(Other definitions for lair that I've seen before include "Hideaway, den" , "Flashy man" , "Waylay" , "Place of seclusion (informal)" , "Habitat of a wild animal" .)