17ac)Poetic forger's aid is also beastly. (7)
I have ANDVILE
However if this is correct, then 13 down is lettered as follows..
-ANE-OO-E
13d)G-gag over sentimentality and almost get a hopeless case(9, two words)
-ANE-OO-E
Although LAME GOOSE was suggested to me , this would make ANDVILE into AMD-IL-
(Anyway,the phrase is LAME DUCK , isn't it?)