It's no good running (13)
I believe the answer is:
mismanagement
'running' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'it's no good' is the wordplay.
I cannot really see how this works, but
'no' could be 'n' (common abbreviation) and 'n' is found within the answer.
'good' could be 'g' (abbreviation) and 'g' is located in the answer.
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for mismanagement that I've seen before include "Poor stewardship" , "Bad running (of company)" , "Bad running (of something)" , "Poor running" , "Maladministration" .)