I came a cross the expression かげぐち【陰口】(backbiting) and found it in my dictionary as follows
人の陰口をきく[たたく]|[speak ill of a person / run a person down] behind his back / backbite
When I tried to look up the meaning of きく the only transitive verbs that seem possible are 聞く& 聴く. However these relate to listening or at best "asking" which does not seem to be quite same thing.
Should I just accept such expressions as idioms? Even if that is the correct course it seems odd that the entry for 聞く does not mention this use.