10 5/9/34/30D/7/35/4/1D is a poem quoted in full in ODQ. The author’s surname (and indeed first name) appears at 26.
 

Across

1    Portable furniture affected county (8, hyphened)
8    It’s only fair (4)
12    Get ready to improve shepherd’s delight left in champagne? (10)
13    Some twin sisters are demanding (6)
14    Book wrapping was double Scotch? (7)
15    Chemical engineer rejects classical dry measures (8)
18    Awfully insecure time for those lacking control? (9)
19    Spenser’s bound to study in plant (9)
20    Genuinely caught the criminal (4)
21    Votes against heartless bills in US (4)
24    In Monaco I break a contract, lacking hearts and diamonds? (6)
27    Fever therefore masks...