An aristocrat who swings both ways is not quite right (1,3,3)
I believe the answer is:
a bit off
'not quite right' is the definition.
'an aristocrat who swings both ways' is the wordplay.
I cannot really understand how this works, but
'an' could be 'i' (Roman numeral for one) and 'i' is found in the answer.
'aristocrat' could be 'toff' (toff can mean an upper-class person) and 'toff' is present in the answer.
The remaining letters 'ab' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'is' acts as a link.
Can you help me to learn more?
(Other definitions for a bit off that I've seen before include "in poor taste" , "In bad taste" , "unacceptable!" , "Small discount" , "a small reduction in price" .)