McCartney possibly excellent right away (6)
I believe the answer is:
stella
'mccartney possibly' is the definition.
(Stella McCartney is a fashion designer)
'excellent right away' is the wordplay.
I cannot really understand how this works, but
'away' could be 'a' (abbreviation as used in sports fixtures) and 'a' is located in the answer.
The remaining letters 'stell' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for stella that I've seen before include "lady?" , "Paul McCartney's daughter" , "Girl's name meaning star" , "Swift favourite" , "- Gibbons (Cold Comfort Farm)" .)