I know miss struggles crossing river -- this could describe the situation (4,2,4)
I believe the answer is:
sink or swim
'this could describe the situation' is the definition.
(as in a sink or swim situation)
'i know miss struggles crossing river' is the wordplay.
'struggles' is an anagram indicator.
'crossing' indicates putting letters inside.
'river' becomes 'r' (abbreviation for river).
'i'+'know'+'miss'='iknowmiss'
'iknowmiss' is an anagram of 'sinkoswim'.
'sinkoswim' enclosing 'r' is 'SINK OR SWIM'.
(Other definitions for sink or swim that I've seen before include "Do/die strategy" , "Survive (or not) by one's own efforts" , "Cope (or not) unaided" , "To succeed or fail (the only options!)" .)