Bracket shape (3)
I believe the answer is:
ell
'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 measure equivalent to about 45 inches in England" , "Embellish with old measure of length" , "railway in Chicago?" , "Length of cloth" , "Old measurement" .)