Creatures ordered to rest (6)
I believe the answer is:
otters
'creatures' is the definition.
'ordered to rest' is the wordplay.
'ordered' indicates an anagram.
'to'+'rest'='torest'
'torest' with letters rearranged gives 'OTTERS'.
(Other definitions for otters that I've seen before include "Fish-eating mammals" , "Water animals with webbed feet and flat tails" , "Or test out these mammals" , "Sleek short-furred swimmers" , "Aquatic carnivores" .)