Tries to get into authentic attire to lead final run (5,9)
I believe the answer is:
dress rehearsal
'final run' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'tries to get into authentic attire to lead' is the wordplay.
'tries' becomes 'hears' (as in trying or hearing in a trial).
'to get into' means one lot of letters goes inside another.
'authentic' becomes 'real' (authentic means real or genuine).
'attire' becomes 'dress' (synonyms).
'to lead' means one lot of letters go next to another.
'hears' going within 'real' is 'rehearsal'.
'rehearsal' put after 'dress' is 'DRESS REHEARSAL'.
Can you help me to learn more?
(Other definitions for dress rehearsal that I've seen before include "trial run" , "Final play run-through" , "last chance to get things right" , "last practice" , "Strip show doesn't need such" .)