What does the cryptic crossword clue "Dropping in Nana, Barrie's first dog, for surgery (10)" mean?

The definition is "Dropping". The wordplay uses an anagram. anagram of IN NANA B DOG = ABANDONING; definition: "Dropping" The answer is ABANDONING.

Dropping in Nana, Barrie's first dog, for surgery (10)

Times Cryptic #29151 | 4 Across | 2025-02-12 flower