Find one's about to enter port (8)
I believe the answer is:
discover
'find' is the definition.
(I know that find is a more specific form of discover)
'one's about to enter port' is the wordplay.
'one's about' becomes 'isc' (I can't explain this - if you can you should believe this answer much more).
'to enter' means one lot of letters goes inside another.
'port' becomes 'dover' (English port).
'isc' going inside 'dover' is 'DISCOVER'.
Can you help me to learn more?
(Other definitions for discover that I've seen before include "Be first to observe" , "Show up" , "Uncover, find" , "Be the first to find something" , "Be the first to have sight or knowledge of" .)