Some stockbrokers set up shelter (3)
I believe the answer is:
cot
'shelter' is the definition.
(I've seen this in other clues)
'some stockbrokers set up' is the wordplay.
'some' says the answer is hidden in the clue (some parts of the word are used).
'set up' says the letters should be written backwards (in a down clue, letters go up).
'toc' is hidden within 'stockbrokers'.
'toc' reversed gives 'COT'.
(Other definitions for cot that I've seen before include "Folding bed - fingerstall" , "Small boat to hold a baby" , "Camp bed" , "Small bed with high sides" , "baby carrier?" .)