What does the cryptic crossword clue "In shop, Tim is this person with a half-full glass? (8)" mean?

The wordplay uses a hidden word. Hidden [ in ] "sh OP TIM IS T his" The answer is OPTIMIST.

In shop, Tim is this person with a half-full glass? (8)

Guardian Cryptic #29561 | 17 Down | 2024-12-09 flower