Latticework goes from treetops back to sill (7)
I believe the answer is:
trellis
'latticework' is the definition.
(I've seen this before)
'goes from treetops back to sill' is the wordplay.
'goes from treetops' becomes 'tre' (I can't justify this - if you can you should give a lot more credence to this answer).
'back' shows that the letters should be reversed in order.
'sill' written backwards gives 'llis'.
'tre'+'llis'='TRELLIS'
Can you help me to learn more?
(Other definitions for trellis that I've seen before include "Garden climber support" , "Framework for creepers" , "Garden frame or screen" , "Light framework for climbing plants" , "Train for plants" .)