Laid car out, being thorough (7)
I believe the answer is:
radical
'being thorough' is the definition.
(as in a radical or thorough overhaul of something)
'laid car out' is the wordplay.
'out' is an anagram indicator (out can mean wrong or inaccurate).
'laid'+'car'='laidcar'
'laidcar' is an anagram of 'RADICAL'.
(Other definitions for radical that I've seen before include "Thoroughgoing - (popularly) extremist" , "Fundamental - non-conformist" , "Progressive; extreme" , "Political extremist" , "Militant" .)