Wan publican's first drink (4)
I believe the answer is:
pale
'wan' is the definition.
(I know that wan can be written as pale)
'publican's first drink' is the wordplay.
'publican's first' becomes 'p' (ast letter of 'publican').
'drink' becomes 'ale' (type of beer).
'p'+'ale'='PALE'
(Other definitions for pale that I've seen before include "picket" , "Colourless" , "wooden post" , "Not bright - limit" , "Ashen" .)