What does the cryptic crossword clue "Some fumes enter all old parts of the gut (9)" mean?

The definition is "parts of the gut". The wordplay uses a hidden word. Hidden in "some fuMES ENTER All old parts of the gut" The answer is MESENTERA.

Some fumes enter all old parts of the gut (9)

Guardian Cryptic #28953 | 15 Across | 2022-12-29 flower