The unclued lights can be paired in some way or other. One is of two words.
 

Across

1    Distrain a dog brutally leading to loss of status (12)
10    Deep blue of Mediterranean ‘îles’ (4)
14   When this fish turns, it’s not fit for eating (3)
17    Pays attention to journalist when he’s around (5)
18    ‘Let It Be’ almost ruined with inclusion of classy little singer (7, two words)
19    Trees that appear to be almost uncharted (6)
22    Love in a home on the water (6)
24    Fellow back in police custody (5)
26    Such a company about to get by, with Conservative’s behind (9)
27    Economic deficits –...