Lame cooking with ordinary recipe, ultimately humdrum grub (8)
I believe the answer is:
mealworm
'grub' is the definition.
(mealworm is a type of insect larva or grub)
'lame cooking with ordinary recipe ultimately humdrum' is the wordplay.
'cooking' indicates anagramming the letters (cook can mean to falsify or distort).
'with' becomes 'w' (abbreviation).
'ordinary' becomes 'O' (abbreviation e.g. O-Levels).
'recipe' becomes 'r' (abbreviation in medical prescriptions).
'ultimately' indicates one should take the final letters.
The final letter of 'humdrum' is 'm'.
'lame' is an anagram of 'meal'.
'meal'+'w'+'o'+'r'+'m'='MEALWORM'
(Other definitions for mealworm that I've seen before include "Beetle larva" , "larva disliked by millers" .)