Harmless sort of tiger may be decorative on the wall (5)
I believe the answer is:
paper
I believe this is a double definition.
'harmless sort of tiger' is the first definition.
(a paper tiger is something harmless or ineffective)
'may be decorative on the wall' is the second definition.
(wallpaper)
(Other definitions for paper that I've seen before include "News publication" , "Government report" , "Treatise" , "It's usually made from wood pulp" , "Material made from wood pulp, say" .)