In back of island, time to pass off (5)
I believe the answer is:
foist
'pass off' is the definition.
(I've seen this before)
'in back of island time' is the wordplay.
'in back of island' becomes 'fo' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'time' becomes 'ist' (I've seen this in other clues).
'fo'+'ist'='FOIST'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for foist that I've seen before include "Pass off, impose (on)" , "palm off" , "Impose, inflict" , "Cause person to accept something unwelcome or unwanted" , "Impose (upon)" .)