The unclued lights (two of two words), individually or as one pair, are of a kind.
 

Across

9    City call that reverberates (4)
11    A bouncer from evil European, reportedly (9, two words)
12    The Times with leaders only advocating German economic safeguards (4)
17    Explosive sounds of large swallows (5)
20    Petty quarrel – one with a student about room (7)
21    Scully’s partner hiding love for modeller? (7)
25    Colours of birds surrounding top of nest (5)
26    Landowner in Scottish mire died (5)
31    Sailing boats departed taking three directions (7)
34    Admissions of debt by scamp lacking respect (7)
37    Pet about to return, so put out food?...