Body of water in city that is conversely smack in the middle (8)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

Body of water in city that is conversely smack in the middle KEER (REEK (=smack (of), small strongly (of); “conversely” indicates reversal) in [L.A. (=city, i.e. Los Angeles) + I.E. (=that is, id est)]