Curiously, Aristotelean refuses loan while writing dissertation (8)
I believe the answer is:
treatise
'dissertation' is the definition.
(I've seen this before)
'curiously aristotelean refuses loan' is the wordplay.
'curiously' is an anagram indicator.
'refuses' suggests deleting specific letters.
'aristotelean' with 'loan' taken out is 'ristteea'.
'ristteea' is an anagram of 'TREATISE'.
'while writing' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for treatise that I've seen before include "Tract, monograph" , "Written work dealing with one subject" , "Formal written work dealing with a particular subject" , "Systematically-written formal piece" , "Formal piece of writing on a particular subject" .)