What does the cryptic crossword clue "Dull common hero requiring makeover (10)" mean?

The definition is "Dull". The wordplay uses an anagram. anagram of COMMON + HERO = MONOCHROME; definition: "Dull" The answer is MONOCHROME.

Dull common hero requiring makeover (10)

Daily Mail Cryptic #17316 | 25 Across | 2024-03-18 flower