What does the cryptic crossword clue "Rescued from incredibly deep river (9)" mean?

The definition is "Rescued". The wordplay uses an anagram. anagram of DEEP + RIVER = REPRIEVED; definition: "Rescued" The answer is REPRIEVED.

Rescued from incredibly deep river (9)

Independent Cryptic #1644 | 24 Across | 2021-08-29 flower