Edge with radius one metre (3)
I believe the answer is:
rim
'edge' is the definition.
(rim is a kind of edge)
'with radius one metre' is the wordplay.
'with' is a charade indicator (letters next to each other).
'radius' becomes 'r' (abbreviation in geometry).
'one' becomes 'i' (Roman numeral).
'metre' becomes 'm' (synonyms).
'r' put next to 'i' is 'ri'.
'ri'+'m'='RIM'
(Other definitions for rim that I've seen before include "Top edge" , "Outer edge of a wheel" , "Circular outer edge" , "Edge - lip" , "Circumference" .)