Drink, taking in a French dawn (5)
I believe the answer is:
sunup
'dawn' is the definition.
(I know that dawn can be written as sunup)
'drink taking in a french' is the wordplay.
'drink' becomes 'sup' (to sup is to drink).
'taking in' means one lot of letters goes inside another.
'a french' becomes 'un' ('a' in French).
'sup' going around 'un' is 'SUNUP'.
(Other definitions for sunup that I've seen before include "First light (US), rhymes with travelling over one hundred mph" , "Solar appearance (US)" , "Dawn (American)" , "Daybreak (in America)" , "Dawn (mainly US)" .)