Take unnecessary risk parking next to lawyer if hit, possibly (4,4,4)
I believe the answer is:
play with fire
'take unnecessary risk' is the definition.
(to play with fire is to take a risk)
'parking next to lawyer if hit possibly' is the wordplay.
'parking' becomes 'p' (abbreviation on road signs).
'next to' means one lot of letters go next to another.
'possibly' indicates anagramming the letters.
'lawyer'+'if'+'hit'='lawyerifhit'
'lawyerifhit' anagrammed gives 'laywithfire'.
'p'+'laywithfire'='PLAY WITH FIRE'
(Other definitions for play with fire that I've seen before include "Live dangerously" , "feel the heat?" , "Put oneself in danger" , "Be open to risk" , "Promethean drama?" .)