Difficult to reverse into narrow Italian traffic restriction (5,5)
I believe the answer is:
speed limit
'traffic restriction' is the definition.
(restriction vehicles)
'difficult to reverse into narrow italian' is the wordplay.
'difficult' becomes 'deep' (difficult can mean deep or obscure).
'to reverse' shows that the letters should be reversed in order.
'into' indicates putting letters inside.
'narrow' becomes 'slim' (I've seen this in another clue).
'italian' becomes 'it' (abbreviation for Italian).
'deep' reversed gives 'peed'.
'peed' placed within 'slim' is 'speedlim'.
'speedlim'+'it'='SPEED-LIMIT'
(Other definitions for speed limit that I've seen before include "Fine results maybe after exceeding this" , "permitted maximum velocity?" , "Flashily ignoring this may gain you points" , "Driving restriction" , "Maximum MPH allowed on a particular road" .)