Teacher back in one British pub (5)
I believe the answer is:
rabbi
'teacher' is the definition.
(I've seen this in another clue)
'back in one british pub' is the wordplay.
'back' is a reversal indicator.
'in one' becomes 'i' (Roman numeral. I am not sure about the 'in' bit.).
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'pub' becomes 'bar' (both are drinking establishments).
'i'+'b'+'bar'='ibbar'
'ibbar' written backwards gives 'RABBI'.
Can you help me to learn more?
(Other definitions for rabbi that I've seen before include "Jewish religious teacher" , "A Jewish clergyman" , "Blue" , "Leader of worshippers" , "Jewish law expounder" .)