Ring road is a major operation (6)
I believe the answer is:
bypass
This could be a double definition.
'ring road' is the first definition.
(synonyms)
'major operation' is the second definition.
'bypass' can be an answer for 'operation' (I've seen this before). I am unsure of the 'major' bit.
'is a' acts as a link.
Can you help me to learn more?
(Other definitions for bypass that I've seen before include "ring-road, maybe" , "Go round (congested area etc)" , "Go around" , "not found in the high street" , "What avoids Newbury" .)