Their scaly form may be hilarious (10)
I believe the answer is:
hysterical
'be hilarious' is the definition.
(thesaurus)
'their scaly form' is the wordplay.
'form' is an anagram indicator.
'their'+'scaly'='theirscaly'
'theirscaly' with letters rearranged gives 'HYSTERICAL'.
'may' acts as a link.
(Other definitions for hysterical that I've seen before include "Violently emotional" , "Over-emotional" , "Emotionally unstable" , "Uncontrollably laughing or crying" , "Wildly funny" .)