What does the cryptic crossword clue "Elders possibly seen in Montmartre establishment (5)" mean?

The definition is "Elders". The wordplay uses a hidden word. Hidden in "elders possibly seen in montmarTRE EStablishment" The answer is TREES.

Elders possibly seen in Montmartre establishment (5)

Guardian Cryptic #29037 | 6 Down | 2023-04-06 flower