Temperature upset leaders in Haiti and another tropical island (6)
I believe the answer is:
tahiti
'tropical island' is the definition.
'tahiti' can be an answer for 'island' (Tahiti is an example). I'm unsure of the 'tropical' bit.
'temperature upset leaders in haiti and another' is the wordplay.
'temperature' becomes 't' (abbreviation).
'upset' shows that the letters should be reversed in order.
'leaders' says to take the initial letters.
'another' becomes 'ti' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The initial letters of 'in haiti and' is 'iha'.
'iha' backwards is 'ahi'.
't'+'ahi'+'ti'='TAHITI'
(Other definitions for tahiti that I've seen before include "part of Polynesia" , "South Seas island, capital Papeete" , "I hit at the tropical island" , "Polynesian island where Gauguin lived" , "Gauguin's Pacific isle" .)