A vet disturbed over service in bar (6)
I believe the answer is:
tavern
'bar' is the definition.
(thesaurus)
'a vet disturbed over service' is the wordplay.
'disturbed' indicates anagramming the letters.
'over' means one lot of letters goes inside another.
'service' becomes 'rn' (abbreviation for Royal Navy).
'vet' is an anagram of 'tve'.
'a' placed inside 'tve' is 'tave'.
'tave'+'rn'='TAVERN'
'in' acts as a link.
(Other definitions for tavern that I've seen before include "Old song: 'There is a ...... in the town, in the town'" , "An old inn, musically in the town" , "Tap house" , "Old-fashioned word for pub" , "drinking establishment" .)