Spout stupidly on top of rotunda, in a daze (6)
I believe the answer is:
stupor
'in a daze' is the definition.
(I've seen this before)
'spout stupidly on top of rotunda' is the wordplay.
'stupidly' indicates anagramming the letters.
'on top of' says to take the initial letters (I've seen 'on top' mean this).
The first letter of 'rotunda' is 'r'.
'spout' with letters rearranged gives 'stupo'.
'stupo'+'r'='STUPOR'
(Other definitions for stupor that I've seen before include "Dazed or unconscious condition, sometimes caused by alcohol" , "state of somnolence" , "lethargic" , "Proust found in dazed condition" , "mental dullness?" .)