Work too hard concerning tune (10)
I believe the answer is:
overstrain
'work too hard' is the definition.
(I've seen this in another clue)
'concerning tune' is the wordplay.
'concerning' becomes 'over' (both can mean relating to).
'tune' becomes 'strain' (synonyms).
'over'+'strain'='OVERSTRAIN'
(Other definitions for overstrain that I've seen before include "too much exercise may produce this" , "Tax" .)