What does the cryptic crossword clue "Her Nibs used to take a dip here (7)" mean?

The definition is "Her Nibs used to take a dip here". The wordplay uses a cryptic definition. Cryptic definition The answer is INKWELL.

Her Nibs used to take a dip here (7)

Guardian Cryptic #29184 | 26 Across | 2023-09-25 flower