What does the cryptic crossword clue "Modification of clue in central parts (6)" mean?

The definition is "central parts". The wordplay uses an anagram. anagram of CLUE + IN = NUCLEI; definition: "central parts" The answer is NUCLEI.

Modification of clue in central parts (6)

Daily Mail Cryptic #17591 | 23 Down | 2025-04-07 flower