Entertain chap with beer (6)
I believe the answer is:
regale
'entertain' is the definition.
(I've seen this before)
'chap with beer' is the wordplay.
'chap' becomes 'reg' ().
'with' means one lot of letters go next to another.
'beer' becomes 'ale' (type of beer).
'reg'+'ale'='REGALE'
(Other definitions for regale that I've seen before include "Lavishly supply" , "Feast, give pleasure to" , "Entertain lavishly" , "Fete" , "Amuse with stories" .)