Coat with brown material (6)
I believe the answer is:
tartan
'material' is the definition.
(tartan is a kind of material)
'coat with brown' is the wordplay.
'coat' becomes 'tar' (tarring is a kind of coating).
'with' says to put letters next to each other.
'brown' becomes 'tan' (tan is a kind of brown).
'tar'+'tan'='TARTAN'
(Other definitions for tartan that I've seen before include "Scots material" , "Cloth with a crisscross design" , "Criss-cross pattern" , "Distinctive pattern of Highland clan as seen in kilt" , "Scots patterned cloth" .)