Crouch down, sit on one's heels (5)
I believe the answer is:
squat
I believe this clue is a double definition.
'crouch down' is the first definition.
(I've seen this in another clue)
'sit on one's heels' is the second definition.
(I've seen this in another clue)
(Other definitions for squat that I've seen before include "hunch" , "Refuse to move on" , "Compact" , "Short, low" , "Crouch with bent knees" .)