Support publicity work (4)
I believe the answer is:
prop
'support' is the definition.
(prop up can mean to support)
'publicity work' is the wordplay.
'publicity' becomes 'pr' (abbreviation for public relations).
'work' becomes 'op' (common abbreviation for 'opus').
'pr'+'op'='PROP'
(Other definitions for prop that I've seen before include "Temporary support" , "Support; rugby forward" , "player involved in scrum" , "Shore for 4 down" , "Front row forward" .)