Rule in favour of one country? Totally heartless (9)
I believe the answer is:
formality
'rule' is the definition.
(thesaurus)
'in favour of one country? totally heartless' is the wordplay.
'in favour of' becomes 'for' (being for a particular cause).
'one country?' becomes 'mali' (Mali is an example).
'heartless' suggests removing the centre.
'totally' with its centre taken out is 'ty'.
'for'+'mali'+'ty'='FORMALITY'
(Other definitions for formality that I've seen before include "ceremony" , "Social rigidity" , "Stiffness" , "Established convention" .)