Start to saw wood for window frame (4)
I believe the answer is:
sash
'window frame' is the definition.
(I've seen this in another clue)
'start to saw wood' is the wordplay.
'start to' suggests taking the first letters.
'wood' becomes 'ash' (wood from an ash tree).
The initial letter of 'saw' is 's'.
's'+'ash'='SASH'
'for' acts as a link.
(Other definitions for sash that I've seen before include "Window frame; cloth strip (worn over shoulder)" , "seen hanging around Miss World?" , "Ribbon worn over the shoulder" , "Decorative belt" , "Baldrick" .)