Special quality of vote for accepting parliamentary bill (1-6)
I believe the answer is:
x factor
'special quality' is the definition.
(I've seen this before)
'vote for accepting parliamentary bill' is the wordplay.
'vote' becomes 'x' (how votes are marked).
'accepting' means one lot of letters goes inside another.
'parliamentary bill' becomes 'act'.
'for' placed around 'act' is 'factor'.
'x'+'factor'='X-FACTOR'
'of' is the link.
(Other definitions for x factor that I've seen before include "military hardship payment" , "Its judges hear appalling submissions" , "Noteworthy special talent" , "Magical 'something'" , "Indefinable special quality" .)