Mediterranean island reported big growth (7)
I believe the answer is:
cypress
'big growth' is the definition.
(large tree or plant)
'mediterranean island reported' is the wordplay.
'mediterranean island' becomes 'cyprus' (I've seen this before).
'reported' shows a homophone (sound like).
'cyprus' sounds like 'CYPRESS'.
(Other definitions for cypress that I've seen before include "Conifer, symbol of mourning" , "one rooted in the Med?" , "Coniferous tree" , "Evergreen, mourning symbol" , "One living in churchyard" .)