Street's manifest disuse under motorway entrance to Indian reservations (8)
I believe the answer is:
mistrust
'reservations' is the definition.
(I've seen this before)
'street's manifest disuse under motorway entrance to indian' is the wordplay.
'street' becomes 'st' (abbreviation).
'manifest disuse' becomes 'rust' (I can't justify this - if you can you should believe this answer much more).
'under' says to put letters next to each other (in a down clue, some letters go below others).
'motorway' becomes 'M' (as in motorway names - Mr, Mt etc).
'entrance to' suggests taking the first letters.
The initial letter of 'indian' is 'i'.
'st'+'rust'='strust'
'm'+'i'='mi'
'strust' put after 'mi' is 'MISTRUST'.
Can you help me to learn more?
(Other definitions for mistrust that I've seen before include "Suspect (someone)" , "Have doubts about" , "Regard with suspicion" , "Lack of belief (in someone)" , "reservations" .)