Manage after hearing test (5,3)
I believe the answer is:
trial run
'test' is the definition.
(I have seen 'Introductory test' mean 'trial run' so perhaps 'test' could also mean 'trial run')
'manage after hearing' is the wordplay.
'manage' becomes 'run' (both can mean to organise).
'after' means one lot of letters go next to another.
'hearing' becomes 'trial' (I've seen this before).
'run' put after 'trial' is 'TRIAL RUN'.
(Other definitions for trial run that I've seen before include "Experimental outing" , "Turn rail around in practical test" , "'Preliminary test of how something works (5,3)'" , "Test drive" , "Test mission" .)