Fish for an ancient settler in Britain (5)
I believe the answer is:
angle
'fish for' is the definition.
(thesaurus)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for angle that I've seen before include "may be right" , "Early settler" , "member of tribe" , "Glean (anag.)" , "A way of approaching" .)