League of nations reticent with German involved (6)
I believe the answer is:
comity
'league of nations' is the definition.
Both the definition and answer are singular nouns.
Maybe you can see an association between them that I don't see?
'reticent with german involved' is the wordplay.
'reticent' becomes 'coy' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'with german' becomes 'mit' ('with' in German).
'involved' means one lot of letters goes inside another.
'coy' going around 'mit' is 'COMITY'.
Can you help me to learn more?
(Other definitions for comity that I've seen before include "Courteousness" , "Civilised state of affairs" , "Politeness" , "Civility" .)