Farewell drink served after five (4)
I believe the answer is:
vale
'farewell' is the definition.
(I've seen this before)
'drink served after five' is the wordplay.
'drink' becomes 'ale' (type of beer).
'served after' says to put letters next to each other.
'five' becomes 'V' (Roman numeral).
'ale' after 'v' is 'VALE'.
(Other definitions for vale that I've seen before include "'''Sweet ... of Avoca, how calm could I rest'' (Moore) (4)'" , "Maida -, N. London area; farewell (archaic)" , "Trough between ridges" , "Glen; goodbye!" , "Cheers" .)