Theatre worker on edge composing stirring song (8,6)
I believe the answer is:
national anthem
'song' is the definition.
(national anthem is a kind of song)
'theatre worker on edge' is the wordplay.
'theatre' becomes 'national' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'worker' becomes 'ant' (worker is a type of ant).
'on' says to put letters next to each other.
'edge' becomes 'hem' (I've seen this in another clue).
'national'+'ant'+'hem'='NATIONAL ANTHEM'
'composing stirring' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for national anthem that I've seen before include "The Marseillaise, perhaps" , "noted stirrer" , "The Star-Spangled Banner', say" , "country air" , "Patriotic song" .)