Where Luke is found, or Frank (8)
I believe the answer is:
postmark
'frank' is the definition.
(synonyms)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for postmark that I've seen before include "It shows date and time of mailing" , "Letter franking" , "Stamp franking" , "It is stamped on envelope" , "Frank" .)