Time for one obscure worry? No time (9)
I believe the answer is:
dimension
'time for one' is the definition.
(time is a kind of dimension)
'obscure worry? no time' is the wordplay.
I cannot really understand how this works, but
'obscure' could be 'dim' (I've seen this before) and 'dim' is present in the answer.
'no' could be 'o' (resembles 0 - 'no' can mean 'zero') and 'o' is found within the answer.
This explanation may well be incorrect...
(Other definitions for dimension that I've seen before include "measure" , "Proportion" , "size" , "Length or breadth, say" .)