"Mount", as used in street names (4)
I believe the answer is:
etna
'mount' is the definition.
(Etna is an example)
'used in street names' is the wordplay.
'used in' indicates the answer is hidden within the clue.
'ETNA' can be found hidden inside 'street names'.
'as' acts as a link.
(Other definitions for etna that I've seen before include "It could erupt" , "Heating vessel" , "it may produce steam and ash" , "Sicilian volcano" , "Sicily's 15" .)