There could be some royal fiddlers! (5)
I believe the answer is:
three
'there could be some royal fiddlers' is the definition.
I can't judge whether this defines the answer.
'there could be' is the wordplay.
'could be' indicates an anagram.
'there' is an anagram of 'THREE'.
Can you help me to learn more?
(Other definitions for three that I've seen before include "Number constituting a crowd?" , "Prime number" , "Small number that still makes a crowd?" , "Amount in a trio" , "Subject of 1 9" .)