Part of window made from special wood (4)
I believe the answer is:
sash
'part of window' is the definition.
(part of a window frame)
'special wood' is the wordplay.
'special' becomes 'S' (common abbreviation as in Special Air Service).
'wood' becomes 'ash' (wood from an ash tree).
's'+'ash'='SASH'
'made from' acts as a link.
(Other definitions for sash that I've seen before include "Cummerbund" , "Band worn over shoulder or round waist" , "Item of clothing - frame for glass" , "Baldrick" , "Framework to hold the panes of a window" .)