Outlandish request -- go mad (9)
I believe the answer is:
grotesque
'outlandish' is the definition.
(thesaurus)
'request go mad' is the wordplay.
'mad' indicates anagramming the letters.
'request'+'go'='requestgo'
'requestgo' with letters rearranged gives 'GROTESQUE'.
(Other definitions for grotesque that I've seen before include "Outlandish" , "Comically ugly" , "Freakish" , "Fantastically hideous" , "Bizarre and disfigured - preposterous" .)