They are seen regularly in Gulf Coast (6,7)
I believe the answer is:
flying saucers
'they' is the definition.
Both the answer and definition are plural nouns.
Perhaps they are linked in a way I don't understand?
'are seen regularly in gulf coast' is the wordplay.
I cannot quite understand how this works, but
'are' could be 'a' (short for 'are', historical unit of measurement) and 'a' is located in the answer.
'in' is within the answer.
'gulf' could be 'g' (geographical abbreviation) and 'g' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for flying saucers that I've seen before include "UFOs" , "Extraterrestrial objects, apparently observed by some people" .)