Rim of band in iron (6)
I believe the answer is:
fringe
'rim' is the definition.
(thesaurus)
'band in iron' is the wordplay.
'band' becomes 'ring' ('ring' can be a synonym of 'band').
'in' is an insertion indicator.
'iron' becomes 'fe' (Fe is the chemical symbol for iron).
'ring' put inside 'fe' is 'FRINGE'.
'of' is the link.
(Other definitions for fringe that I've seen before include "Border; not mainstream" , "Border; marginal" , "Border - unofficial festival events" , "Border, outer part" , "Perimeter" .)