Watering hole buffaloes and rhinos initially used (3)
I believe the answer is:
bar
'watering hole' is the definition.
(watering hole can mean a drinking establishment)
'buffaloes and rhinos initially used' is the wordplay.
'initially used' suggests taking the first letters.
The initial letters of 'buffaloes and rhinos' is 'BAR'.
(Other definitions for bar that I've seen before include "Support (for a drinker?)" , "Pub; restriction" , "Rigid piece of metal" , "Pole" , "Counter; prevent" .)