What does the cryptic crossword clue "This could be raised to part of mouth (3)" mean?

The definition is "mouth". The wordplay uses a reversal. GUM (reversal="part of the mouth") = MUG; definition: "mouth" The answer is MUG.

This could be raised to part of mouth (3)

Guardian Cryptic #28148 | 17 Down | 2020-06-01 flower