With river flooding in, send for solution to problem (4-3)
I believe the answer is:
cure-all
'solution to problem' is the definition.
(cure for a problem)
'with river flooding in send for' is the wordplay.
'with' indicates putting letters inside.
'river' becomes 'r' (abbreviation for river).
'flooding' becomes 'ue' (I can't justify this - if you can you should give a lot more credence to this answer).
'in' is an insertion indicator.
'send for' becomes 'call' (synonyms).
'r' going within 'ue' is 'ure'.
'ure' inserted within 'call' is 'CURE-ALL'.
(Other definitions for cure-all that I've seen before include "Universal remedy" , "Universal panacea" , "Panacea, nostrum" .)