A king amid excited fans at palace quite unruffled (4,2,1,7)
I believe the answer is:
flat as a pancake
'quite unruffled' is the definition.
(very flat or unruffled)
'a king amid excited fans at palace' is the wordplay.
I cannot quite understand how this works, but
'a' could be 'an' and 'an' is found within the answer.
'king' could be 'k' (chess abbreviation) and 'k' is present in the answer.
'at' is present in the answer.
This explanation may well be incorrect...
(Other definitions for flat as a pancake that I've seen before include "So utterly dead" , "battery output?" , "Not at all uneven" .)