Copper, possibly who became young partner of Pinkerton's (9)
I believe the answer is:
butterfly
'copper possibly' is the definition.
(I know that copper is a type of lycaenid)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for butterfly that I've seen before include "Winged insect and swimming stroke" , "Idea that a small change can have major consequences elsewhere" , "Lepidopterous insect" , "Swimming stroke - sort of net, kiss or screw" , "Insect with four coloured wings and feelers" .)