Keen on country pitch (10)
I believe the answer is:
intonation
'pitch' is the definition.
(thesaurus)
'keen on country' is the wordplay.
'keen on' becomes 'into' (I've seen this before).
'country' becomes 'nation' (synonyms).
'into'+'nation'='INTONATION'
(Other definitions for intonation that I've seen before include "Feature of speech" , "Rise and fall in voice pitch" , "bit of plainsong" .)