Bog paper defines shareholders’ meeting (8)
I believe the answer is:
quagmire
'bog' is the definition.
(quagmire is a kind of bog)
'paper defines shareholders' meeting' is the wordplay.
'paper' becomes 'quire' (paper measurement).
'defines' means one lot of letters goes inside another (to define can mean to create a boundary or outline).
'shareholders' meeting' becomes 'agm' (abbreviation for annual general meeting).
'quire' enclosing 'agm' is 'QUAGMIRE'.
(Other definitions for quagmire that I've seen before include "You can get bogged down in this" , "Swampy marsh" , "Here one is bogged down" , "Boggy ground" , "Bog; complex situation" .)