Labour lag behind with introduction of alternative vote? (7)
I believe the answer is:
travail
'labour' is the definition.
(travail is a kind of labour)
'lag behind with introduction of alternative vote?' is the wordplay.
'lag behind' becomes 'trail' (I've seen this before).
'with' means one lot of letters goes inside another.
'introduction of' says to take the initial letters.
The first letters of 'alternative vote' is 'av'.
'trail' going around 'av' is 'TRAVAIL'.
(Other definitions for travail that I've seen before include "painful exercise" , "Exertion, elbow grease" , "Use of physical or mental energy; excessive labour..." , "Old word for pangs of childbirth" , "Hard labour" .)