Believe to be a regular visitor to our shores (7)
I believe the answer is:
swallow
'believe' is the definition.
(swallowing is a kind of believing)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for swallow that I've seen before include "Bird - gulp down" , "Fork-tailed bird" , "flier" , "Migrating bird" , "One of these does not make a spring" .)