Busker's last to occupy sofa in squat (6)
I believe the answer is:
crouch
'squat' is the definition.
(I've seen this before)
'busker's last to occupy sofa' is the wordplay.
'last' says to take the final letters.
'to occupy' means one lot of letters goes inside another (I've seen this in other clues).
'sofa' becomes 'couch' ('couch' can be a synonym of 'sofa').
The last letter of 'busker' is 'r'.
'r' placed within 'couch' is 'CROUCH'.
'in' is the link.
(Other definitions for crouch that I've seen before include "Bent knees posture" , "Stoop with knees bent" , "Prepare to spring" , "Lower the body with bent knees as if about to spring" , "Hunker down" .)