What does the cryptic crossword clue "Intro a liar concocted is unfounded (10)" mean?

The wordplay uses an anagram. anagram of INTRO + A + LIAR = IRRATIONAL The answer is IRRATIONAL.

Intro a liar concocted is unfounded (10)

Daily Mail Cryptic #17229 | 23 Across | 2023-11-15 flower