Wall bracket shape (3)
I believe the answer is:
ell
'wall bracket shape' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ell that I've seen before include "Old unit of length" , "Length of cloth" , "Embellish with old measure of length" , "Extension" , "Old measure of length about 45 inches" .)