Grub round small henhouse (5)
I believe the answer is:
roost
'henhouse' is the definition.
(I've seen this before)
'grub round small' is the wordplay.
'grub' becomes 'root' (I've seen this before).
'round' means one lot of letters goes inside another.
'small' becomes 's' (abbreviation - e.g. clothes size).
'root' placed around 's' is 'ROOST'.
(Other definitions for roost that I've seen before include "Bird's night-time perch" , "Bird's settling place" , "residence" , "somewhere to sleep" , "Hen's resting place" .)