Prehistoric Scots concerned with rounding cape and island (7)
I believe the answer is:
ancient
'prehistoric' is the definition.
(I've seen this in another clue)
'scots concerned with rounding cape and island' is the wordplay.
'scots concerned with' becomes 'anent' (Scottish term meaning 'about').
'rounding' indicates putting letters inside (some letters go round others).
'cape' becomes 'c' (abbreviation used on maps).
'and' is a charade indicator (letters next to each other).
'island' becomes 'i' (geographical abbreviation).
'c'+'i'='ci'
'anent' enclosing 'ci' is 'ANCIENT'.
(Other definitions for ancient that I've seen before include "showing signs of wear?" , "Antiquated" , "Nice tan (anag.)" , "Belonging to a former age" , "Pistol" .)