I may ring a wrong sort of number (9)
I believe the answer is:
imaginary
'sort of number' is the definition.
'i may ring a wrong' is the wordplay.
'wrong' indicates anagramming the letters.
'may'+'ring'+'a'='mayringa'
'mayringa' is an anagram of 'maginary'.
'i'+'maginary'='IMAGINARY'
(Other definitions for imaginary that I've seen before include "Illusory" , "Not real" , "Not based on fact, unreal" , ""All in the mind"" , "Fancied" .)