Garden-dweller keeps abbreviated book on source of dahlias unfolded (7)
I believe the answer is:
evolved
'unfolded' is the definition.
The definition and answer can be both related to change as well as being past participle verbs.
Perhaps you can see an association between them that I can't see?
'garden-dweller keeps abbreviated book on source of dahlias' is the wordplay.
'garden dweller' becomes 'eve' (I've seen this in another clue).
'keeps' indicates putting letters inside (inserted letters are kept inside).
'abbreviated book' becomes 'vol' (short for volume. I am not sure about the 'abbreviated' bit.).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'source of' says to take the initial letters (the start - or source - of the word).
The initial letter of 'dahlias' is 'd'.
'eve' placed around 'vol' is 'evolve'.
'evolve'+'d'='EVOLVED'
Can you help me to learn more?
(Other definitions for evolved that I've seen before include "Developed and changed very gradually" , "Advanced" , "Underwent development" , "Gradually developed as Darwin put it" , "Undergone stages of development" .)