Opening wooden instruments to cut plant (4,6)

'opening' is the definition.
(a window is an opening)

'wooden instruments to cut plant' is the wordplay.
'wooden' becomes 'ash' (made of ash).
'instruments' becomes 'wind' (wind section of an orchestra).
'to cut' indicates putting letters inside (some letters cut their way into a word).
'plant' becomes 'sow' ().
'ash'+'wind'='ashwind'
'ashwind' placed into 'sow' is 'SASH-WINDOW'.