Lengthy duet performed after one gets coordinate (9)
I believe the answer is:
longitude
'coordinate' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'lengthy duet performed after one' is the wordplay.
'lengthy' becomes 'long' (synonyms).
'performed' indicates an anagram.
'after' is a charade indicator (letters next to each other).
'one' becomes 'i' (Roman numeral).
'duet' anagrammed gives 'tude'.
'tude' after 'i' is 'itude'.
'long'+'itude'='LONGITUDE'
'gets' is the link.
Can you help me to learn more?
(Other definitions for longitude that I've seen before include "Distance in degrees" , "this helps define our position" , "Degree from Greenwich" , "Distance east or west of the Greenwich meridian" , "Imaginary circles of distance east or west" .)