Odd street across the mountains (7)
I believe the answer is:
strange
'odd' is the definition.
(I've seen this before)
'street across the mountains' is the wordplay.
'street' becomes 'st'.
'across' says to put letters next to each other (across can mean on).
'the mountains' becomes 'range' (I've seen this before).
'st'+'range'='STRANGE'
(Other definitions for strange that I've seen before include "Odd or unknown" , "Out of the ordinary" , "Slightly odd, a bit weird" , "Odd, peculiar" , "Bizarre" .)