Witness provided, one residing in another street (9)
I believe the answer is:
testifier
'witness' is the definition.
(I know that testifier is a type of witness)
'provided one residing in another street' is the wordplay.
'provided' becomes 'if' (eg 'provided it's sunny' means 'if it's sunny').
'one' becomes 'i' (Roman numeral).
'residing in' is an insertion indicator.
'another' indicates anagramming the letters.
'if'+'i'='ifi'
'street' with letters rearranged gives 'tester'.
'ifi' inserted into 'tester' is 'TESTIFIER'.
(Other definitions for testifier that I've seen before include "One acknowledging" , "person in court?" , "One who may declare" , "Witness" .)