Bone sample from hospital useful (5)
I believe the answer is:
talus
'bone' is the definition.
(talus is a kind of bone)
'sample from hospital useful' is the wordplay.
'sample from' says the answer is hidden in the clue (a sample of letters from the clue).
'TALUS' is hidden in the letters of 'hospital useful'.
(Other definitions for talus that I've seen before include "Ankle bone" , "Yarns" , "Foot's part" , "Ankle-bone" .)