Until now, therefore, playing a round in (10)
I believe the answer is:
heretofore
'until now' is the definition.
(I've seen this in another clue)
'therefore playing a round in' is the wordplay.
I cannot really see how this works, but
'round' could be 'o' (o is a circular letter) and 'o' is present in the answer.
an anagram of 'therefore' is 'heretfore' which is located in the remaining letters.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for heretofore that I've seen is " Up to now".)