Left motorway during Italian restriction (5)
I believe the answer is:
limit
'restriction' is the definition.
(thesaurus)
'left motorway during italian' is the wordplay.
'left' becomes 'l' (common abbreviation).
'motorway' becomes 'mi' (resembles M1, English motorway).
'during' indicates putting letters inside.
'italian' becomes 'it'.
'mi' going inside 'it' is 'imit'.
'l'+'imit'='LIMIT'
(Other definitions for limit that I've seen before include "Restrict to specified range" , "Place bound on" , "verge" , "Curb" , "Constrain" .)