Erect border, forbidding one making the hajj? (7)
I believe the answer is:
pilgrim
'one making the hajj?' is the definition.
(the Hajj is the Islamic pilgrimage to Mecca)
'erect border forbidding' is the wordplay.
'erect' shows that the letters should be reversed in order.
'border' becomes 'lip' (I've seen this in other clues).
'forbidding' becomes 'grim' (I've seen this before).
'lip' in reverse letter order is 'pil'.
'pil'+'grim'='PILGRIM'
(Other definitions for pilgrim that I've seen before include "One of those who sailed to New England in the Mayflower, 1620" , "One progressive type" , "Seeker" , "One travelling to a sacred place" , "Traveller (who made Progress?)" .)