Building material for a little pig (5)
I believe the answer is:
straw
'building material for a little pig' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for straw that I've seen before include "Residue of cereal crop" , "Stems left after grain has been removed" , "Bedding material for horses etc" , "In the wind, it's an indication" , "Dried grain stalks" .)