16 Down - answer is "revamp", so 24 Across - answer is "partner" !
Preface has seven letters and starts with a p.
America
Conduit.
utterer,
Both Andorra and Antigua start with A and have seven letters.
Darshan and duramen are the seven letters word that start with D and end with N.
It's not seven but eight letters: republic.
Estelle
tobilsium
Brittany
Absolutely no idea. Sorry.
cowhide