Bikini, possibly, demanding a tax (5)
I believe the answer is:
atoll
'bikini possibly' is the definition.
(Bikini Atoll is an example)
'a tax' is the wordplay.
'tax' becomes 'toll' (I've seen this in other clues).
'a'+'toll'='ATOLL'
'demanding' acts as a link.
(Other definitions for atoll that I've seen before include "Ring-shaped coral reef enclosing a lagoon" , "land threatened by rising sea levels" , "tropical island" , "Coral circle" , "Bikini, say" .)