Winning group staying in key (13)
I believe the answer is:
prepossessing
'winning' is the definition.
(I've seen this before)
'group staying in key' is the wordplay.
I cannot quite see how this works, but
'group' could be 'posse' and 'posse' is present in the answer.
'in' is within the answer.
'key' could be 'g' (musical key) and 'g' is present in the answer.
The remaining letters 'press' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for prepossessing that I've seen before include "Attractive" , "Fetching" , "winning" , "looking good" .)