‘1D/19’ (six words in total) is a work by 18/13. Remaining unclued lights form two pairs suggested by 13.
 

Across

 
1    Rhubarb hems in humungous hen house (5)
10    Sweeteners in course lass sprinkled (10)
11    I tease one who’s arrived clasping book (6)
14    Engaging earl retired Russian spots (5)
15    Seconds served with the Spanish wine (5)
16    Old fruit trees housing yellow songbird (6)
22    Pacific route carrying navy quarterly (8)
23    Abnormal growth spoiling Andromeda doctor removed (7)
24    No English song (Breton possibly) (3)
25    Crow’s greeting baby owl let out (3)
27    Hero stimulated woeful bishop (7)
29    Steamy ball, a thousand going — I like pole...