Small trained group (5)
I believe the answer is:
cadre
'small trained group' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for cadre that I've seen before include "Core group -- cared (anag)" , "Political group" , "Group of key personnel" , "Raced around with basic military unit" , "Raced (anag) - small central group" .)