Collected some medical materials (4)
I believe the answer is:
calm
'collected' is the definition.
(I've seen this before)
'some medical materials' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'CALM' is hidden within 'medical materials'.
(Other definitions for calm that I've seen before include "Tranquil, undisturbed" , "Windless" , "Imperturbable, soothe" , "Unruffled, not excited" , "Pacific" .)