Bill's outing in street through evergreen Berkshire town (5,7)
I believe the answer is:
first reading
'bill's outing' is the definition.
(as in a parliamentary bill)
'street through evergreen berkshire town' is the wordplay.
'street' becomes 'st' (abbreviation).
'through' means one lot of letters goes inside another (inserted letters go through the word).
'evergreen' becomes 'fir' (I've seen this before).
'berkshire town' becomes 'Reading' (Reading is a town in Berkshire).
'fir'+'reading'='firreading'
'st' inserted within 'firreading' is 'FIRST READING'.
'in' is the link.
(Another definition for first reading that I've seen is " Bill's initial appearance".)