The wood is left brown (6)
I believe the answer is:
lumber
'the wood' is the definition.
(I've seen this before)
'left brown' is the wordplay.
'left' becomes 'l' (common abbreviation).
'brown' becomes 'umber' (umber is a kind of brown).
'l'+'umber'='LUMBER'
'is' is the link.
(Other definitions for lumber that I've seen before include "Unwanted furniture" , "Sawn wood ready for use" , "Move clumsily - Jack's wood?" , "Sawn timber" , "Move awkwardly - unwanted household items" .)