Five unclued lights are connected with one partner, four with the other. Another links both.

Across

1    Nervous about yarn being threadbare (6)
11    She intervenes, announcing press deceptions (9)
12    Currency heretic returns (5)
14    Saviour’s foul-up: I take fright, losing head (9)
16    Switch middle of tracks for competitions (6)
21    ‘Estimates’ (6)
22    Joins college team with backing (6)
24    New serum transformed little Oz birds (3,5)
26    Track aircraft losing pressure (4)
27    Detailed plan for fish (3)
28    NZ native a little like Australian (3)
29    Some Nigerians find one chief a bit off (4)
32    Not free to resort to special water additive (8)
34    Wit has energy to...