What does the cryptic crossword clue "Ernest cannot change trains here (6,6)" mean?

The wordplay uses an anagram. anagram of ERNESTCANNOT ("Ernest cannot") [anagram: "change"] = CANNONSTREET The answer is CANNONSTREET.

Ernest cannot change trains here (6,6)

Guardian Cryptic #24781 | 11 Across | 2009-08-18 flower