Ruling about turning up is unacceptable (9)
I believe the answer is:
repugnant
'unacceptable' is the definition.
(repugnant means unacceptable or disgusting)
'ruling about turning up' is the wordplay.
'ruling' becomes 'regnant' (as in a queen regnant, a queen who rules by birth).
'about' indicates putting letters inside.
'turning' indicates anagramming the letters.
'up' anagrammed gives 'pu'.
'regnant' going around 'pu' is 'REPUGNANT'.
'is' is the link.
(Other definitions for repugnant that I've seen before include "revolting" , "Disgusting" , "Nasty" , "vile" , "Very unwelcome" .)