Request space and agreement (8)
I believe the answer is:
entreaty
'request' is the definition.
(I know that entreaty is a type of request)
'space and agreement' is the wordplay.
'space' becomes 'en' (in printing, a space as wide as a letter 'n').
'and' says to put letters next to each other.
'agreement' becomes 'treaty' (treaty is a kind of agreement).
'en'+'treaty'='ENTREATY'
(Other definitions for entreaty that I've seen before include "suit" , "Earnest or urgent request" , "application for assistance" , "Appeal" , "Supplication" .)