"Oh, Mom, can I go on the train and see him [Harry Potter], Mom, eh please…."
"You've already seen him, Ginny, and the poor boy isn't something you goggle at in a zoo. Is he really, Fred? How do you know?"
"Asked him. Saw his scar. It's really there – like lightning."
"Poor dear – no wonder he was alone, I wondered. He was ever so polite when he asked how to get onto the platform."
(Harry Potter and the Sorcerer's Stone)
What does dear mean? (It seems an exclamation; yet it is after the adjective poor. It's not proper to call it. So it could be pointing "Harry Potter".)
Best Answer
I can't find any online dictionary definitions exactly matching the intended sense here, but I'll just mention that OED has dear = Dear one, darling.
It's only loosely connected to the "exclamatory" version in "Oh dear! What can the matter be?"
Much more relevant is "Dear Fred" as the introduction to a letter. Rowling's usage is certainly common in BrE, particularly from mothers and grandmothers. Essentially, adjectival dear = cherished, valued, loved is being used as noun (one who is cherished, valued, loved).
Note that in this context, poor = unfortunate. "Poor dear!" is a common expression indicating sympathy and affection - often for a child (or someone being treated as a child), who is suffering in some way.