What does the cryptic crossword clue "Immaculate as Swiss cheese, we hear? (4)" mean?

The definition is "Immaculate". The wordplay uses a homophone (sounds like). sounds like 'holey'="as Swiss cheese, we hear?" The answer is HOLY.

Immaculate as Swiss cheese, we hear? (4)

Guardian Cryptic #29293 | 18 Across | 2024-01-31 flower