Opposite motorway, under a Gormley (7)
I believe the answer is:
antonym
'opposite' is the definition.
(synonyms)
'motorway under a gormley' is the wordplay.
'motorway' becomes 'm'.
'under' means one lot of letters go next to another.
'a gormley' becomes 'antony' (I can't explain this - if you can you should believe this answer much more).
'm' put after 'antony' is 'ANTONYM'.
Can you help me to learn more?
(Other definitions for antonym that I've seen before include "opposing description" , "A word opposite in meaning to another" , "One's import is contrary" , "Word that means the opposite of another" , "As 'happy' is to 'sad' or 'long' to 'short'" .)