A line of footwear (8)
I believe the answer is:
plimsoll
This clue is a double definition.
'a line' is the first definition.
(Plimsoll is an example)
'footwear' is the second definition.
(plimsoll is a kind of footwear)
'of' is the link.
(Other definitions for plimsoll that I've seen before include "Pump social reformer" , "Shipping legislator" , "Sports shoe; a line" , "Mark on ship's side to indicate limit of loading" , "Light gym shoe and waterline" .)