Work steadily, hosting a performance (4)
I believe the answer is:
play
'performance' is the definition.
(performance in a theatre)
'work steadily hosting a' is the wordplay.
'work steadily' becomes 'ply' (as in plying one's trade).
'hosting' is an insertion indicator.
'ply' going around 'a' is 'PLAY'.
(Other definitions for play that I've seen before include "Scope - entertainment" , "Perform music" , "Make sport" , "Slack - performance" , "See 17" .)