The most common and most likely answer to this crossword clue is the 9 letter word SOMMELIER
I've seen this crossword clue in The Daily Telegraph
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More clues leading to the result SOMMELIER
- Amazingly memorise taste of Liebfraumilch? One might
- Smile more after tickling a steward of Burgundy?
- Expert on drinking has battle with organ, though not heart
- Wine waiter’s romance, in embrace of German actress
- Wine waiter right after start of meal in a certain lounge
- Somehow memorise litres to be carried? He may have to
- Ordering rosé? Me, I’m left to translate!
- Expert waiting, one down in the WWI trenches?
- Smile more fake, as wine waiter
- Restaurant worker in battle that is grasped by both hands
Buddy explains!

The straight part
We know that "steward" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case steward = sommelier.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does SOMMELIER mean?
SOMMELIER noun- The member of staff at a restaurant who keeps the wine cellar and advises the guests on a choice of wines; a wine steward / stewardess, a wine waiter / waitress / server.
- To act as a sommelier.