Blimey — hemmed in by river in both directions! (3-3)
I believe the answer is:
two-way
'blimey hemmed in by river in both directions' is the definition.
I can't judge whether this defines the answer.
'hemmed in by river in both directions' is the wordplay.
'hemmed in by' is an insertion indicator.
'river' becomes 'tay' (Scottish river).
'in both directions' becomes 'wow' (I am not sure about this - if you are sure you should believe this answer much more).
'tay' placed around 'wow' is 'TWO-WAY'.
Can you help me to learn more?
(Other definitions for two-way that I've seen before include "Involving movement in either direction" , "Involving reciprocation" .)