OS showing circuitous routes? (6)
I believe the answer is:
rounds
I believe this is a double definition.
'os' is the first definition.
(round can mean a round object like an O)
'circuitous routes?' is the second definition.
(circular journeys)
'showing' acts as a link.
(Other definitions for rounds that I've seen before include "Sections of boxing matches" , "Charges of ammunition or drinks for everyone" , "Journeys to successive customers" , "18 holes of golf and boxing bouts, say" , "periods of fighting" .)