Doctor Seuss' extremely loopy novel (7)
I believe the answer is:
ulysses
'novel' is the definition.
(James Joyce novel)
'doctor seuss' extremely loopy' is the wordplay.
'doctor' indicates an anagram.
'extremely' suggests removing the centre (only the extremes of the word are used).
'loopy' with its middle taken out is 'ly'.
'seuss'+'ly'='seussly'
'seussly' anagrammed gives 'ULYSSES'.
(Other definitions for ulysses that I've seen before include "work" , "Latin form of Odysseus" , "-- S. Grant, US President" , "Famous novel by James Joyce" , "Hero of the Odyssey and James Joyce title" .)