Forms fungi (6)
I believe the answer is:
moulds
I believe this clue is a double definition.
'forms' is the first definition.
(I know this)
'fungi' is the second definition.
(mould is a kind of fungus)
(Other definitions for moulds that I've seen before include "Frames for clay, wax, etc" , "Hollow shapes for molten liquid material" , "Forms something out of malleable material" , "Causes to have a certain shape or character" , "Containers into which liquid is poured to create shapes" .)