Roofing material for brood on top of tree (6)
I believe the answer is:
thatch
'roofing material' is the definition.
(thatch is a kind of roofing material)
'brood on top of tree' is the wordplay.
'brood' becomes 'hatch' ('hatch' can be a synonym of 'brood').
'on' is a charade indicator (letters next to each other).
'top of tree' becomes 't' (I can't explain this - if you can you should give a lot more credence to this answer).
'hatch' after 't' is 'THATCH'.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for thatch that I've seen before include "Old fashioned rural roof covering" , "Material used to cover" , "Natural roof cover" , "Use plant stalks as roofing" , "Old roofing material" .)