Less familiar route followed by US commando (8)
I believe the answer is:
stranger
'less familiar' is the definition.
(I've seen this before)
'route followed by us commando' is the wordplay.
'route' becomes 'st' (abbreviation for street).
'followed by' says to put letters next to each other.
'us commando' becomes 'ranger' (I can't justify this - if you can you should believe this answer much more).
'st'+'ranger'='STRANGER'
Can you help me to learn more?
(Other definitions for stranger that I've seen before include "Someone unfamiliar" , "Person one doesn't know" , "Truth can be ... than fiction" , "Non-acquaintance" , "Regrants oddly to person unknown" .)