Fifth of November is pigsty, full of messy ash - grotesque (9)
I believe the answer is:
misshapen
'grotesque' is the definition.
(thesaurus)
'fifth of november is pigsty full of messy ash' is the wordplay.
'fifth of november' becomes 'm' (5th letter of 'november').
'pigsty' becomes 'pen' (I've seen this in another clue).
'full of' means one lot of letters goes inside another.
'messy' is an anagram indicator.
'is'+'pen'='ispen'
'ash' with letters rearranged gives 'sha'.
'ispen' enclosing 'sha' is 'isshapen'.
'm'+'isshapen'='MISSHAPEN'
(Other definitions for misshapen that I've seen before include "Unnaturally formed" , "Not looking round" , "Badly formed" , "Ugly in form" , "showing bad form" .)