Declare in a tavern (4)
I believe the answer is:
aver
'declare' is the definition.
(averring is a kind of declaring)
'in a tavern' is the wordplay.
'in' says the answer is hidden in the clue.
'AVER' is hidden in the letters of 'tavern'.
(Other definitions for aver that I've seen before include "'Affirm, assert (4)'" , "Declare or insist" , "Firmly maintain" , "claim" , "State decisively" .)