Tool seen in small insanitary dwelling (6)
I believe the answer is:
shovel
'tool' is the definition.
(shovel is a kind of tool)
'small insanitary dwelling' is the wordplay.
I cannot quite understand how this works, but
'small' could be 's' (abbreviation - e.g. clothes size) and 's' is located in the answer.
'dwelling' could be 'hovel' (I have seen 'Wretched dwelling' mean 'hovel' so perhaps 'dwelling' could also mean 'hovel') and 'hovel' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'seen in' is the link.
Can you help me to learn more?
(Other definitions for shovel that I've seen before include "Tool like a spade" , "something for digs" , "Spade-like tool" , "Spade with a curved blade" , "Tool to be found in hovels?" .)