Slope did twist - it's not straight (8)
I believe the answer is:
lopsided
'it's not straight' is the definition.
I can't tell whether this defines the answer.
'slope did twist' is the wordplay.
'twist' is an anagram indicator (a twisted or distorted version of the letters).
'slope'+'did'='slopedid'
'slopedid' anagrammed gives 'LOPSIDED'.
Can you help me to learn more?
(Other definitions for lopsided that I've seen before include "Not symmetrical" , "With one part lower or heavier than the other" , "Crooked" , "Askew, awry" , "Unbalanced" .)