Islanders win at sea, unexpectedly leading English (9)
I believe the answer is:
taiwanese
'islanders' is the definition.
(the people of Taiwan, an island)
'win at sea unexpectedly leading english' is the wordplay.
'unexpectedly' indicates an anagram.
'leading' indicates taking the first letters (the leading letter of the word).
The initial letter of 'english' is 'e'.
'win'+'at'+'sea'='winatsea'
'winatsea' anagrammed gives 'taiwanes'.
'taiwanes'+'e'='TAIWANESE'
(Other definitions for taiwanese that I've seen before include "Asian" , "Islander" , "Oriental type" , "from Asia" , "Chinese" .)