Illuminated about large road restriction (5)
I believe the answer is:
limit
'restriction' is the definition.
(I've seen this before)
'illuminated about large road' is the wordplay.
'illuminated' becomes 'lit' (synonyms).
'about' means one lot of letters goes inside another.
'large road' becomes 'mi' (resembles M1 motorway. I am not sure about the 'large' bit.).
'lit' going around 'mi' is 'LIMIT'.
Can you help me to learn more?
(Other definitions for limit that I've seen before include "qualify?" , "Utmost" , "Keep in" , "Constrain" , "verge" .)