Most inspired lines about Iowa animal book (8)
I believe the answer is:
bestiary
'animal book' is the definition.
(a bestiary is a book about animals)
'most inspired lines about iowa' is the wordplay.
'most inspired' becomes 'best' (most inspired or brilliant).
'lines' becomes 'ry' (abbreviation for railway).
'about' means one lot of letters go next to another.
'iowa' becomes 'IA' (abbreviation).
'ry' put after 'ia' is 'iary'.
'best'+'iary'='BESTIARY'
(Other definitions for bestiary that I've seen before include "Medieval collection of descriptions of animals" , "medieval treatise" , "Allegorical work" , "Medieval book of animals for sybarite" , "Medieval collection of animal descriptions for sybarite" .)