Seed perhaps mine, though not a tree, ultimately (5)
I believe the answer is:
pulse
'seed' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for pulse that I've seen before include "Healthy food" , "Rhythmical throb of arteries" , "Heart-throb" , "Heart rhythm" , "Pound" .)