Copy a girl, sadly (4)
I believe the answer is:
alas
'sadly' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for alas that I've seen before include "What a shame!" , "Regretfully!" , "Expression of grief/pity" , "Interjection of sorrow" , "Exclamation of misfortune" .)