Imprecise in former legislation (7)
I believe the answer is:
inexact
'imprecise' is the definition.
(associated in meaning)
'in former legislation' is the wordplay.
'former' becomes 'ex' (prefix meaning former or onetime).
'legislation' becomes 'act' (I've seen this in other clues).
'in'+'ex'+'act'='INEXACT'
(Other definitions for inexact that I've seen before include "Not quite accurate" , "Imprecise - inaccurate in" , "Woolly" , "Rough" , "estimated?" .)