What does the cryptic crossword clue "Causing criminal damage, a rail company at fault (12)" mean?

The wordplay uses an anagram. anagram of ARAILCOMPANY ("a rail company") [anagram: "at"] = PYROMANIACAL The answer is PYROMANIACAL.

Causing criminal damage, a rail company at fault (12)

Guardian Cryptic #23907 | 21 Across | 2006-10-26 flower