The unclued lights (one of two words), individually or as two pairs, are of a kind. Elsewhere, ignore one accent.
 

Across

1           Groups of helpers providing accompaniments to pop-singers (8)
5           Trembling like fish (6)
14         Some weekend supplement (3)
16         Lionel wrecked ornamental metalwork (6)
17         Pack animal in a shopping plaza from the east (5)
18         Climber following others’ lead, like a sheep (5)
20         Early satellite rattles around (7)
22         Minerva regularly gripped by desire to win (7)
24         Scandalous episode of trade show in unopened eatery (7)
25         Clans parking in groups (5)
26         Toss last bit of pepper into casserole (5)
28         Flies second in six going west (7)
31        ...