Telling when a river's banks ran through the country (9)
I believe the answer is:
narration
'telling' is the definition.
(I've seen this before)
'a river's banks ran through the country' is the wordplay.
'banks' says to hollow out the word (remove centre letters) (the sides or banks of the word).
'ran' is an anagram indicator (letters have run around).
'through' is an insertion indicator (I've seen this in other clues).
'the country' becomes 'nation' ('nation' can be a synonym of 'country').
'river' with its middle taken out is 'rr'.
'a'+'rr'='arr'
'arr' with letters rearranged gives 'rra'.
'rra' inserted into 'nation' is 'NARRATION'.
'when' is the link.
(Other definitions for narration that I've seen before include "Story" , "Voice-over in film" , "Process of storytelling" , "Spoken account" , "Account of events" .)