Trellis strip (4)
I believe the answer is:
lath
'trellis strip' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lath that I've seen before include "Thin wood strip supporting plaster" , "Wooden strip for plaster" , "Narrow thin strip of wood" , "Narrow strip of wood used as backing for plasterwork" , "Plaster-supporting wood strip" .)