Staunch scientific subjects (4)
I believe the answer is:
stem
'staunch' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for stem that I've seen before include "Shoot; arrest" , "Slender upright part, of flower or wineglass" , "Slender vertical part, glass or plant" , "feature of wine glass" , "part of vegetable?" .)