Wooden, like roof of house (3)
I believe the answer is:
ash
'wooden' is the definition.
(made of ash)
'like roof of house' is the wordplay.
'like' becomes 'as'.
'roof of' says to take the initial letters (in a down clue, the roof is the top letter).
The initial letter of 'house' is 'h'.
'as'+'h'='ASH'
(Other definitions for ash that I've seen before include "Remains from the yule-log?" , "In fireplace it may be" , "Tree in danger" , "Common tree" , "End of fire" .)