Conclude model on French Island is nonproductive? (9)
I believe the answer is:
'nonproductive?' is the definition.
'conclude model on french island' is the wordplay.
'conclude' becomes 'infer' (inferring is a kind of concluding).
'model' becomes 't' (Ford Model T car).
'on' means one lot of letters go next to another.
'french island' becomes 'ile' ('island' in French).
'is' is the link.
(Other definitions for infertile that I've seen before include "So can't father" , "Barren" , "Fruitless" , "Not productive" .)