Contributing to erosion around island (4)
I believe the answer is:
iona
'island' is the definition.
(I've seen this before)
'contributing to erosion around' is the wordplay.
'contributing to' says the answer is hidden in the clue.
'IONA' can be found hidden inside 'erosion around'.
(Other definitions for iona that I've seen before include "Macbeth's resting" , "Christian settlement" , "Inner Hebridean island" , "one in Inner Hebrides" , "Scots monastery isle" .)