What does the cryptic crossword clue "The solid foundations of Cicero's speech? (5,5)" mean?

The definition is "The solid foundations of Cicero’s speech?". The wordplay uses a cryptic definition. Cryptic definition The answer is TERRA FIRMA.

The solid foundations of Cicero's speech? (5,5)

Times Cryptic #29015 | 4 Down | 2024-09-06 flower