Disabled, and one is excused from voting (8)
I believe the answer is:
impaired
'disabled' is the definition.
(I've seen this in another clue)
'one is excused from voting' is the wordplay.
'one is' becomes 'I'm' ('one is' can formally or humorously mean 'I am').
'excused from voting' becomes 'paired' (as in pairing in parliament).
'im'+'paired'='IMPAIRED'
'and' acts as a link.
(Other definitions for impaired that I've seen before include "Defective" , "Damaged, marred" , "Caused weakening, damaged" , "handicapped" , "Spoilt" .)