The most common and most likely answer to this crossword clue is the 10 letter word CONCIERGES
I've seen this crossword clue in Independent
C
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Buddy explains!
The straight part
We know that "Hall porters" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case hall porters = concierges.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 CONCIERGES mean?
CONCIERGES noun- One who attends to the wishes of hotel guests.
- One who attends to the maintenance of a building and provides services to its tenants and visitors.