Hoop goes through Iron rim (6)
I believe the answer is:
fringe
'rim' is the definition.
(I've seen this before)
'hoop goes through iron' is the wordplay.
'hoop goes' becomes 'ring' (I can't explain this - if you can you should give a lot more credence to this answer).
'through' means one lot of letters goes inside another (I've seen this in other clues).
'iron' becomes 'Fe' (Fe is the chemical symbol for iron).
'ring' placed into 'fe' is 'FRINGE'.
Can you help me to learn more?
(Other definitions for fringe that I've seen before include "Tasselled edging" , "Border; marginal" , "Border of threads or hair" , "Border; unconventional" , "Outer edge; hair over forehead" .)