What does the cryptic crossword clue "What boozer, on reflection, must welcome? (5)" mean?

The definition is "What". The wordplay uses a reversal. EH (synonym="EH") in RAB (synonym="RAB") = REHAB; definition: "What" The answer is REHAB.

What boozer, on reflection, must welcome? (5)

Guardian Cryptic #29072 | 13 Across | 2023-05-17 flower