It's worth looking at the amount of money for fuel, possibly (6)
I believe the answer is:
eyeful
'it's worth looking at the amount' is the definition.
I can't tell whether this definition defines the answer.
'of money for fuel possibly' is the wordplay.
'of money' becomes 'ey' (I can't explain this - if you can you should give a lot more credence to this answer).
'for' says to put letters next to each other.
'possibly' indicates an anagram.
'fuel' anagrammed gives 'eful'.
'ey'+'eful'='EYEFUL'
Can you help me to learn more?
(Other definitions for eyeful that I've seen before include "beauty!" , "Interesting sight - beautiful woman" , "Long steady look at something" , "Good long look" , "great sight" .)