Relating to the flanks (7)
I believe the answer is:
lateral
(Other definitions for lateral that I've seen before include "One type of thinking" , "Edgeways" , "Towards the side" , "Situated at or extending to the side" , "Side branch" .)
I believe the answer is:
lateral
(Other definitions for lateral that I've seen before include "One type of thinking" , "Edgeways" , "Towards the side" , "Situated at or extending to the side" , "Side branch" .)