Speciation theory right -- success lies in restraint (9)
I believe the answer is:
darwinism
'speciation theory' is the definition.
'Darwinism' can be an answer for 'theory' (Darwinism is a scientific theory). I'm not certain of the 'speciation' bit.
'right success lies in restraint' is the wordplay.
I cannot quite see how this works, but
'right' could be 'ar' (I've seen this in other clues) and 'ar' is found within the answer.
'success' could be 'win' (I've seen this in another clue) and 'win' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for darwinism that I've seen is " Theory of evolution by natural selection".)