Oasis, managed by one behind bars?
I believe the answer is:
watering-hole
'oasis' is the definition.
(I've seen this before)
'managed by one behind bars?' is the wordplay.
I cannot quite see how this works, but
'by' could be 'at' and 'at' is found within the answer.
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for watering-hole that I've seen before include "Public house (found in a desert?)" , "Oasis" , "Drinking place (for animals)" .)