Class gathered round erected shelters (5)
I believe the answer is:
order
'class' is the definition.
(I know this)
'gathered round erected shelters' is the wordplay.
'shelters' says the answer is hidden in the clue.
'erected' shows that the letters should be reversed in order (in a down clue, letters go up).
'redro' is hidden within 'gathered round'.
'redro' reversed gives 'ORDER'.
(Other definitions for order that I've seen before include "See 20" , "Direct - class - instruction" , "Directive for harmony" , "Uniformity or fraternity" , "Direct or requisition" .)