Staunch group of collaborators achieving target of medical research (4,4)
I believe the answer is:
stem cell
'target of medical research' is the definition.
The definition suggests a singular noun which matches the answer.
'staunch group of collaborators' is the wordplay.
'staunch' becomes 'stem' (synonyms).
'group of collaborators' becomes 'cell' (I can't explain this - if you can you should believe this answer much more).
'stem'+'cell'='STEM CELL'
'achieving' is the link.
Can you help me to learn more?
(Other definitions for stem cell that I've seen before include "Versatile building block of life" , "biological germ" , "Undifferentiated unit of life" , "Generalised producer in living organism" , "genetic unit" .)