Islander let seam unravel (7)
I believe the answer is:
maltese
'islander' is the definition.
(I've seen this before)
'let seam unravel' is the wordplay.
'unravel' indicates anagramming the letters (I've seen 'unravelling' mean this).
'let'+'seam'='letseam'
'letseam' is an anagram of 'MALTESE'.
(Other definitions for maltese that I've seen before include "Someone from Valletta?" , "Description of cross" , "The -- Falcon, 1941 film" , "sort of cross" , "Pigeon" .)