Shouts 'Yes!' accepting fifty quid (5)
I believe the answer is:
yells
'shouts' is the definition.
(yelling is a kind of shouting)
'yes accepting fifty quid' is the wordplay.
'accepting' is an insertion indicator (inserted letters are accepted).
'fifty quid' becomes 'll' (I can't explain this - if you can you should give a lot more credence to this answer).
'yes' placed around 'll' is 'YELLS'.
Can you help me to learn more?
(Other definitions for yells that I've seen before include "Screams" , "Shouts loudly" , "Cries out" .)