I'm disgusted by backtracking individual — it's all I can take! (6)
I believe the answer is:
enough
'it's all i can take' is the definition.
'i'm disgusted by backtracking individual' is the wordplay.
'i'm disgusted' becomes 'ugh' (exclamation of disgust).
'by' says to put letters next to each other.
'backtracking' says the letters should be written backwards.
'individual' becomes 'one'.
'one' in reverse letter order is 'eno'.
'ugh' after 'eno' is 'ENOUGH'.
(Other definitions for enough that I've seen before include "An adequate quantity" , "Not wanting" , "As many as necessary" , "Plenty" , "Adequate amount to meet the purpose" .)