The unclued lights, one of two words, and the others when paired are of a kind. One individual unclued light does double duty.
 

Across

1    Women’s painting seen initially returning by tube (5)
4    Look about, right and left, in a jaunty manner (9)
9    Home I leave — priests’ centre’s defining acts of wickedness (10)
11    Give address that’s fancy, not new (5)
12    Porcelain broken, lacking no true copy (7)
16    Trojan horse finally gains access to a stable backwards (6)
21    What is going beyond The Pale? (8)
24    Fair during the 70s (4)
27    Nemesis from Bremerhaven, Germany (7)
28    Fielder at opponent’s ground has to leave quietly...