Astute nuclear lab supplants power at the heart of CND’s aim (10)
I believe the answer is:
discerning
'astute' is the definition.
(thesaurus)
'nuclear lab supplants power at the heart of cnd's aim' is the wordplay.
I cannot really see how this works, but
'at' could be 'in' (synonymous in some cases - eg at school, in school) and 'in' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for discerning that I've seen before include "clever" , "Particular" , "Showing good judgement" , "Making out" , "Unobtrusively perceptive" .)