Heedless wildebeest, raised on grass, scattered fuel (10)

I believe the answer is:

ungrateful

I'm a little stuck... Click here to teach me more about this clue!

'heedless' is the definition.
Both the definition and answer are adjectives. Maybe they are linked in a way I don't understand?

'wildebeest raised on grass scattered fuel' is the wordplay.
'wildebeest' becomes 'gnu' (synonyms).
'raised' says the letters should be written in reverse (going up in a down clue).
'on' indicates putting letters inside (as in clothing 'on' a person).
'grass' becomes 'rat' (both can mean a snitch or informer).
'scattered' indicates an anagram.
'gnu' backwards is 'ung'.
'fuel' anagrammed gives 'eful'.
'rat' inserted into 'eful' is 'rateful'.
'ung'+'rateful'='UNGRATEFUL'

Can you help me to learn more?

(Other definitions for ungrateful that I've seen before include "no thanks" , "Disagreeable" , "Thankless" .)

I've seen this clue in The Independent.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.