Sandwiched between two rivers, what was that valley? (4)
I believe the answer is:
ruhr
'what was that valley?' is the definition.
I can't tell whether this definition defines the answer.
'sandwiched between two rivers' is the wordplay.
'two rivers' means two replacements for 'river'.
'sandwiched' becomes 'uh' (I can't justify this - if you can you should give a lot more credence to this answer).
'between' is an insertion indicator.
'river' becomes 'r' (abbreviation for river).
'river' becomes 'r' (abbreviation for river).
'r'+'r'='rr'
'uh' inserted within 'rr' is 'RUHR'.
Can you help me to learn more?
(Other definitions for ruhr that I've seen before include "Dortmund area?" , "Major industrial region of north-west Germany" , "Part of Germany" , "German industrial zone, river" , "Traditional region of German heavy industry" .)