Crown prince begins with the French drink (6)
I believe the answer is:
tipple
'drink' is the definition.
(tippling is a kind of drinking)
'crown prince begins with the french' is the wordplay.
'crown' becomes 'tip' ('tip' can be a synonym of 'crown'**).
'begins with' indicates taking the first letters (I've seen 'begin with' mean this).
'the french' becomes 'le'.
The initial letter of 'prince' is 'p'.
'tip'+'p'+'le'='TIPPLE'
(Other definitions for tipple that I've seen before include "Paint < pot" , "fall" , "Knock it back" , "Drink constantly in small quantities" , "Be in the habit of drinking" .)