Self-evident Times article turned up with peculiar expressions I’d ignored (9)
I believe the answer is:
'self-evident' is the definition.
'times article turned up with peculiar expressions i'd ignored' is the wordplay.
'times' becomes 'x' (x resembles the multiplication or times sign).
'article' becomes 'a' (English indefinite article).
'turned up' shows that the letters should be reversed in order.
'with peculiar expressions' becomes 'idiomatic' (using particular idioms or phrases).
'ignored' is a deletion indicator.
'xa' in reverse letter order is 'ax'.
'idiomatic' with 'id' taken away is 'iomatic'.
(Other definitions for axiomatic that I've seen before include "Given" , "Pertaining to self-evident truths" , "Accepted" , "Taken for granted" , "Self-evidently true" .)