What does the cryptic crossword clue "Leo in sum spilt a type of paint (8)" mean?

The definition is "paint". The wordplay uses an anagram. anagram of LEO + IN + SUM = EMULSION; definition: "paint" The answer is EMULSION.

Leo in sum spilt a type of paint (8)

Daily Mail Cryptic #17114 | 29 Across | 2023-06-07 flower