15a A West African people developing "our bay" [6]: ----B- I thought it might be an anagram but can't prove anything.
1d Portuguese town's boast: "top grade" [5]: B-A-A
5d A city in Nevada produces heavy metal [7]: M-R-U--
11d Sedimentary rock's initially strong and healthy [5]: S-A-E ? Shale or slate - can't decide which one!
16d Study Yugoslavia's first available cash? [5]: --A-Y
Many thanks in advance for any help - would be much appreciated.