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 before).
'in'+'ex'+'act'='INEXACT'
(Other definitions for inexact that I've seen before include "Not quite accurate" , "Imprecise - inaccurate in" , "Woolly" , "Rough" , "estimated?" .)