Decry faultless service going round the country (7)
I believe the answer is:
slander
'decry' is the definition.
(thesaurus)
'faultless service going round the country' is the wordplay.
'faultless service' becomes 'ser' (I am not sure about this - if you are sure you should believe this answer much more).
'going round' is an insertion indicator (some letters go around others).
'the country' becomes 'land' ('land' can be a synonym of 'country').
'ser' placed around 'land' is 'SLANDER'.
Can you help me to learn more?
(Other definitions for slander that I've seen before include "False malicious spoken statement" , "Malicious speech" , "False or malicious report" , "Damaging statements" , "Malicious gossip" .)