A stretch of Cherbourg rue? (4)
I believe the answer is:
herb
'rue?' is the definition.
(rue is a kind of herb)
'a stretch of cherbourg' is the wordplay.
'a stretch of' says the answer is hidden in the clue (a stretch of letters from the clue).
'HERB' is hidden within 'cherbourg'.
(Other definitions for herb that I've seen before include "Type of plant used in medicine" , "Parsley, for instance" , "Basil, perhaps" , "man's name" , "Medicinal or culinary plant" .)