What does the cryptic crossword clue "Blur face, but so grotesquely (9)" mean?

The definition is "Blur". The wordplay uses an anagram. anagram of FACE, + BUT + SO = OBFUSCATE; definition: "Blur" The answer is Obfuscate.

Blur face, but so grotesquely (9)

Telegraph Prize Cryptic #3030 | 3 Down | 2019-11-17 flower