The unclued four-letter words can be paired in a particular way to form the remaining unclued lights, one of two words. Elsewhere, ignore two accents.
 

Across

1    Border force on bank guarding river (8)
5    View of a hill removed from a magazine (6)
10    Take steps against token performance (10)
12    As a physician, I must conceal ill feeling (6)
16    Composer having business with French joiner (5)
17    French abbot from Swiss city with primitive plough (7)
18    Curved pathway for car (7)
25    Scotland’s own Foreign Department (3)
26    One or two, say, splitting place in tomb (7)
28    Emirates’ manager endlessly in charge in his element! (7)
29   ...