Early poem's second half - reminiscent of Don Juan ? - moving boyfriend's heart (9)
I believe the answer is:
embryonic
'early' is the definition.
(similar in meaning)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for embryonic that I've seen before include "in its earliest stages" , "In the early stages of development" , "In early stage of development" , "In a rudimentary stage" .)