Without agreement, retreat (4)
I believe the answer is:
nook
'retreat' is the definition.
(nook is a kind of retreat)
'without agreement' is the wordplay.
'without' becomes 'no'.
'agreement' becomes 'ok' (I've seen this in other clues).
'no'+'ok'='NOOK'
(Other definitions for nook that I've seen before include "Sheltered and secluded place" , "Sheltered corner" , "Cranny or niche" , "Secluded recess" , "Corner or small recess" .)