Understood origin includes excavated Neanderthals (6)
I believe the answer is:
sensed
'understood' is the definition.
Both the answer and definition are adjectives. Perhaps they are linked in a way I don't understand?
'origin includes excavated neanderthals' is the wordplay.
'origin' becomes 'seed' (seed is a kind of origin).
'includes' indicates putting letters inside.
'excavated neanderthals' becomes 'ns' (I can't justify this - if you can you should believe this answer much more).
'seed' going around 'ns' is 'SENSED'.
Can you help me to learn more?
(Other definitions for sensed that I've seen before include "'Felt, perceived (6)'" , "Felt, had mental impression" , "Felt, tasted, etc" , "Became vaguely aware of (something)" , "Became aware through mental perception or intuition" .)