Not treating instrumental work seriously? (7)
I believe the answer is:
playing
'not treating instrumental' is the definition.
I can't judge whether this definition defines the answer.
'work seriously?' is the wordplay.
'work' becomes 'play' (I have seen 'Dramatic work' mean 'play' so perhaps 'work' could also mean 'play').
'seriously?' becomes 'ing' (I can't justify this - if you can you should give a lot more credence to this answer).
'play'+'ing'='PLAYING'
Can you help me to learn more?
(Other definitions for playing that I've seen before include "Participating in sport" , "Kings, queens etc" , "Where, it was said, the Battle of Waterloo was won" , "on the field" .)