Questionable royal chap dancing around front of palace (10)
I believe the answer is:
apocryphal
'questionable' is the definition.
(similar in meaning)
'royal chap dancing around front of palace' is the wordplay.
'dancing' indicates anagramming the letters.
'around' is an insertion indicator.
'front of' says to take the initial letters.
The initial letter of 'palace' is 'p'.
'royal'+'chap'='royalchap'
'royalchap' anagrammed gives 'apocryhal'.
'apocryhal' placed around 'p' is 'APOCRYPHAL'.
(Other definitions for apocryphal that I've seen before include "probably made-up" , "Fabulous" .)