"Murray has years of experience in family practice, but he is just a fledgling in surgery."
In the above sentence, is fledgling a noun or an adjective? Or, is it both? Is that why both noun and adjective definitions are present in the following Magoosh practice link?
https://gre.magoosh.com/flashcards/vocabulary/basic-words-3/fledgling
Please provide references for your answer, if possible.
P.s. My punctuation needs work. If you notice any punctuation or grammar problems in my question, please say so!