Valley area underneath emptied into rivers (4)
I believe the answer is:
ruhr
'valley area' is the definition.
'ruhr' can be an answer for 'area' (I have seen 'Industrial area' mean 'ruhr' so perhaps 'area' could also mean 'ruhr'). I'm unsure of the 'valley' bit.
'underneath emptied into rivers' is the wordplay.
'emptied' means to remove the middle letters.
'into' means one lot of letters goes inside another.
'rivers' becomes 'rr' (two abbreviations for river).
'underneath' with its centre removed is 'uh'.
'uh' going within 'rr' is 'RUHR'.
Can you help me to learn more?
(Other definitions for ruhr that I've seen before include "Ger. industrial region" , "Rhine tributary, coal district" , "Flower from Germany" , "German industrial zone, river" , "Part of Germany" .)