Discussion item about radius line on a globe (6)
I believe the answer is:
tropic
'discussion item' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'radius line on a globe' is the wordplay.
'radius' becomes 'r' (abbreviation in geometry).
'line' indicates putting letters inside.
'on' becomes 'to'.
'a globe' becomes 'pic' (I can't justify this - if you can you should believe this answer much more).
'r' put within 'to' is 'tro'.
'tro'+'pic'='TROPIC'
'about' is the link.
Can you help me to learn more?
(Other definitions for tropic that I've seen before include "Cancer is one, Capricorn another" , "Line bordering hot region" , "One of two parallels, Cancer or Capricorn" , "Limiting line of torrid zone" , "Parallel of latitude about 25o N or S" .)