Perhaps ruby breast finally seen amongst the robins flying (10)
I believe the answer is:
birthstone
'breast finally seen amongst the robins flying' is the definition.
I can't judge whether this definition defines the answer.
'perhaps ruby' is the wordplay.
'perhaps' becomes 'birth' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'ruby' becomes 'stone' (I've seen this in another clue).
'birth'+'stone'='BIRTHSTONE'
Can you help me to learn more?
(Other definitions for birthstone that I've seen before include "emerald for May, perhaps" , "rock for one's arrival" , "Gem associated with zodiac sign" , "May emerald, say" .)