Right-angle shaped letter (3)
I believe the answer is:
ell
'right-angle shaped letter' 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 "Once, forty-five inches" , "Measure, approx. fourty-five in." , "Extension" , "distance" , "railway in Chicago?" .)