Some tenors appearing in concert, just for now (3,3)
I believe the answer is:
pro tem
'for now' is the definition.
(short for pro tempore, meaning for the time being)
'some tenors appearing in concert' is the wordplay.
'some tenors appearing' becomes 'te' (I can't justify this - if you can you should give a lot more credence to this answer).
'in' means one lot of letters goes inside another.
'concert' becomes 'prom' (abbreviation for promenade concert).
'te' going inside 'prom' is 'PRO TEM'.
'just' acts as a link.
Can you help me to learn more?
(Other definitions for pro tem that I've seen before include "For the time being (Latin abbreviation)" , "For the present" , "Informally, for the time being" , "Temporarily" , "For the time being, to the old Romans in short" .)