Watering hole popular before noon (3)
I believe the answer is:
inn
'watering hole' is the definition.
(both can mean a drinking establishment)
'popular before noon' is the wordplay.
'popular' becomes 'in' ('in' can mean trendy).
'before' is a charade indicator (letters next to each other).
'noon' becomes 'n'.
'in'+'n'='INN'
(Other definitions for inn that I've seen before include "One of Lincoln's" , "Swiss river" , "Hostelry, tavern" , "Old hostelry for travellers" , "Tavern with lodgings" .)