Subject takes right line about the world (6)
I believe the answer is:
tropic
'line about the world' is the definition.
I can't tell whether this defines the answer.
'subject takes right' is the wordplay.
'subject' becomes 'topic' (as in a topic for discussion).
'takes' is an insertion indicator.
'right' becomes 'r' (abbreviation).
'topic' going around 'r' is 'TROPIC'.
Can you help me to learn more?
(Other definitions for tropic that I've seen before include "Line at nearly 23 degrees N or S" , "Imaginary circle on globe" , "Parallel of latitude about 25o N or S" , "Latitude associated with Capricorn or Cancer" , "Line bordering hot region" .)