Covered the outhouse to keep the warmth in (8)
I believe the answer is:
sheathed
'covered' is the definition.
(sheathing is a kind of covering)
'the outhouse to keep the warmth in' is the wordplay.
'the outhouse' becomes 'shed' (I've seen this in other clues).
'to keep the warmth' becomes 'athe' (I am not sure about this - if you are sure you should believe this answer much more).
'in' indicates putting letters inside.
'shed' going around 'athe' is 'SHEATHED'.
Can you help me to learn more?
(Other definitions for sheathed that I've seen before include "Of sword, placed in scabbard" , "Encased in close-fitting covering - say sword" , "put in protective cover" , "in a case like this" , "Covered for protection" .)