Gap giving view of French lake and one French area? (6)
I believe the answer is:
'gap' is the definition.
(lacuna is a kind of gap)
'french lake and one french area?' is the wordplay.
'french lake' becomes 'lac' ('lake' in French).
'and' says to put letters next to each other.
'one french' becomes 'un' ('one' in French).
'giving view of' is the link.
(Other definitions for lacuna that I've seen before include "Blank gap or missing part", "Space in book or manuscript", "A gap, maybe in a book", "A gap, or section missing from a book", "Gap or hiatus".)