Edge of iron clad hoop (6)
I believe the answer is:
fringe
'edge' is the definition.
(I know that fringe is a type of edge)
'iron clad hoop' is the wordplay.
'iron' becomes 'Fe' (Fe is the chemical symbol for iron).
'clad' indicates putting letters inside.
'hoop' becomes 'ring' (synonyms).
'fe' going around 'ring' is 'FRINGE'.
'of' acts as a link.
(Other definitions for fringe that I've seen before include "Less important" , "Border; unconventional" , "Rim" , "Border, outer part" , "Tasselled edging" .)