Sunbather in this atoll (6)
I believe the answer is:
bikini
'this atoll' is the definition.
(I've seen this before)
'sunbather in' is the wordplay.
I cannot really see how this works, but
'in' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for bikini that I've seen before include "A-test atoll - type of wax?" , "Small two-piece bathing suit" , "Minuscule bathing costume for woman" , "Brief bathing costume" , "offering scanty cover" .)