Attack head demonstrating evolutionary survival principle (7)
I believe the answer is:
fitness
'evolutionary survival principle' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'attack head' is the wordplay.
'attack' becomes 'fit' (fit is a kind of attack).
'head' becomes 'ness' (ness is a headland).
'fit'+'ness'='FITNESS'
'demonstrating' acts as a link.
Can you help me to learn more?
(Other definitions for fitness that I've seen before include "State of good health" , "Suitability - health" , "Competence" , "condition" , "Well-being" .)