Small oak, say, at junction in road (6)
I believe the answer is:
street
'road' is the definition.
(I know that road can be written as street)
'small oak say at junction' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'oak say' becomes 'tree' (oak is an example).
'at' says to put letters next to each other.
'junction' becomes 't'.
's'+'tree'+'t'='STREET'
'in' is the link.
(Other definitions for street that I've seen before include "A thoroughfare or public road" , "See 17" , "Tester (anag.)" , "Way; setter (anag.)" , "Urban road" .)