Opens out old ends of petals (7)
I believe the answer is:
expands
'opens out' is the definition.
The answer and definition can be both related to change as well as being verbs in their -s form.
Perhaps they are linked in a way I don't understand?
'old ends of petals' is the wordplay.
'old' becomes 'ex' (prefix meaning former or onetime).
'ends of petals' becomes 'pands' (I can't justify this - if you can you should believe this answer much more).
'ex'+'pands'='EXPANDS'
Can you help me to learn more?
(Other definitions for expands that I've seen before include "Becomes larger" , "gets bigger" , "Enlarges" .)