Wonderful day with client, essentially drinking French wine (6)
I believe the answer is:
divine
'wonderful' is the definition.
(I've seen this before)
'day with client essentially drinking french wine' is the wordplay.
'day' becomes 'd'.
'with' is a charade indicator (letters next to each other).
'essentially' indicates the central letters.
'drinking' is an insertion indicator.
'french wine' becomes 'vin' (I've seen this before**).
The middle letters of 'client' are 'ie'.
'ie' enclosing 'vin' is 'ivine'.
'd'+'ivine'='DIVINE'
(Other definitions for divine that I've seen before include "Guess" , "Of or coming from God" , "Holy" , "Heavenly" , "Very good" .)