Respected leader imposing conditions on island (9)
I believe the answer is:
statesman
'respected leader' is the definition.
(a statesman is a respected political figure)
'imposing conditions on island' is the wordplay.
'imposing conditions' becomes 'states' (I've seen this in another clue. I am not sure about the 'imposing' bit.).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'island' becomes 'Man' (the Isle of Man is an example).
'states'+'man'='STATESMAN'
(Other definitions for statesman that I've seen before include "Leading politician" , "Government minister" , "Experienced politician" , "Distinguished politician" , "Political leader" .)