Fifty university fellows blocking review of book earnings (9)
I believe the answer is:
emolument
'earnings' is the definition.
(thesaurus)
'fifty university fellows blocking review of book' is the wordplay.
'fifty' becomes 'l' (Roman numeral).
'university' becomes 'U' (abbreviation for university).
'fellows' becomes 'men' (fellow can mean a man).
'blocking' is an insertion indicator (block can mean to plug a gap in something).
'review of book' becomes 'emot' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'l'+'u'+'men'='lumen'
'lumen' put within 'emot' is 'EMOLUMENT'.
Can you help me to learn more?
(Other definitions for emolument that I've seen before include "Profit of employment" , "Compensation paid" , "A fee received, salary" , "payment" , "profit results" .)