Club sandwiches have to be nearer the mouth (9)
I believe the answer is:
downriver
'be nearer the mouth' is the definition.
(nearer to the mouth of a river)
'club sandwiches have' is the wordplay.
'club' becomes 'driver' (type of golf club).
'sandwiches' means one lot of letters goes inside another (to sandwich is to block something in).
'have' becomes 'own' (to have something is to own it).
'driver' placed around 'own' is 'DOWNRIVER'.
'to' acts as a link.
(Other definitions for downriver that I've seen before include "near mouth of Thames?" , "going to the coast?" , "over to the sea" , "From source to mouth" .)