Just one Roman poet investing Pliny's capital (9)

I believe the answer is:

impartial

I'm a little stuck... Click here to teach me more about this clue!

'just' is the definition.
(associated in meaning)

'one roman poet investing pliny's capital' is the wordplay.
'one' becomes 'i' (Roman numeral).
'roman poet' becomes 'martial' (I've seen this before. I am not sure about the 'roman' bit.).
'investing' is an insertion indicator (inserted letters are taken in or invested).
'capital' indicates taking the first letters.
The initial letter of 'pliny' is 'p'.
'martial' enclosing 'p' is 'mpartial'.
'i'+'mpartial'='IMPARTIAL'

Can you help me to learn more?

(Other definitions for impartial that I've seen before include "Showing lack of favouritism" , "not taking sides" , "Disinterested" , "Objective" , "Treating all rivals equally" .)

I've seen this clue in The Independent.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.