The French henchman gets some water (6)
I believe the answer is:
lagoon
'some water' is the definition.
(lagoon is a kind of water)
'the french henchman' is the wordplay.
'the french' becomes 'la' (one of the French words for 'the').
'henchman' becomes 'go on' (goon can mean a henchman or accomplice).
'la'+'goon'='LAGOON'
'gets' is the link.
(Other definitions for lagoon that I've seen before include "Body of salt water cut off from the sea" , "Pool" , "Area inside atoll" , "... separating off this water?" , "Body of water cut off from a larger body by a reef" .)