Most delightful form of insect (6)
I believe the answer is:
nicest
'most delightful' is the definition.
(I've seen this in another clue)
'form of insect' is the wordplay.
'form of' is an anagram indicator (the letters need to be in another 'form').
'insect' anagrammed gives 'NICEST'.
(Other definitions for nicest that I've seen before include "most appetising" , "Best" , "Most agreeable" , "I scent in the most pleasant way" , "Most appealing" .)