Hunker down (5)
I believe the answer is:
squat
'hunker down' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for squat that I've seen before include "Crouch - occupy a dwelling illegally - short and stocky" , "Illegally occupy property" , "Stunted - crouch - unlawfully occupied building" , "building taken over" , "hunch" .)