Ply Rex, say, with beer (6)
I believe the answer is:
regale
'ply' is the definition.
(I know that regale is a more specific form of ply)
'rex say with beer' is the wordplay.
'rex' becomes 'R' (abbreviation e.g. GR=George Rex, King George).
'say' becomes 'eg' (both can mean 'for example').
'with' says to put letters next to each other.
'beer' becomes 'ale' (type of beer).
'r'+'eg'+'ale'='REGALE'
(Other definitions for regale that I've seen before include "Amuse with stories" , "Lavishly supply" , "Feast, give pleasure to" , "Entertain royally" , "Entertain with conversation" .)