Application that preserves love like this in Greek island (8)
I believe the answer is:
creosote
'application that preserves' is the definition.
(creosote can be used as a preservative)
'love like this in greek island' is the wordplay.
'love' becomes 'o' (In tennis, 'love' means 'zero').
'like this' becomes 'so'.
'in' indicates putting letters inside.
'greek island' becomes 'crete' (I've seen this before).
'o'+'so'='oso'
'oso' put into 'crete' is 'CREOSOTE'.
(Other definitions for creosote that I've seen before include "Dark oily liquid, preservative for wood" , "'Dark oily liquid, preserves wood (8)'" , "Oily excretion" , "Preserve deal, say" , "Oily, smelly wood preservative" .)