Propositions concerning trade union resolution (9)
I believe the answer is:
overtures
'propositions' is the definition.
(overture is a kind of proposition)
'concerning trade union resolution' is the wordplay.
'concerning' becomes 'over' (both can mean relating to).
'trade union' becomes 'TU' (abbreviation for trade union).
'resolution' becomes 'res' (I've seen this in other clues).
'over'+'tu'+'res'='OVERTURES'
(Other definitions for overtures that I've seen before include "Musical introductions" , "Attempts at seduction" , "Tentative suggestions to elicit reactions" , "Diplomatic advances" , "Orchestral introductions to an opera etc" .)