Bikini Atoll tests gained notoriety after initially going wrong (5)
I believe the answer is:
tanga
'bikini' is the definition.
(a Tanga bikini is a kind of bikini)
'atoll tests gained notoriety after initially going wrong' is the wordplay.
'initially' suggests taking the first letters.
'going wrong' is an anagram indicator.
The first letters of 'atoll tests gained notoriety after' is 'atgna'.
'atgna' anagrammed gives 'TANGA'.
(Other definitions for tanga that I've seen before include "piece of swimwear" , "skimpy garment" , "underwear" , "Skimpy briefs - a gnat (anag)" , "Briefs not covering hips" .)