Ring back to describe island flower (5)
I believe the answer is:
lilac
'flower' is the definition.
(I've seen this before)
'ring back to describe island' is the wordplay.
'ring' becomes 'call' (call on the phone).
'back' says the letters should be written backwards.
'to describe' is an insertion indicator.
'island' becomes 'i' (geographical abbreviation).
'call' back-to-front is 'llac'.
'llac' enclosing 'i' is 'LILAC'.
(Other definitions for lilac that I've seen before include "Tree - pinkish-purple colour" , "garden ornamental" , "Shrub with fragment purple or white flowers" , "I call (anag)" , "Shrub or small tree with fragrant blossom" .)