What does the cryptic crossword clue "They melt and oddly increase with these drifting (3,6)" mean?

The wordplay uses an anagram. ICES (synonym="‘oddly I n C r E a S e’") + HEETS (synonym="HEETS") = ICESHEETS The answer is ICESHEETS.

They melt and oddly increase with these drifting (3,6)

Guardian Cryptic #29477 | 19 Across | 2024-09-02 flower