In this dictionary, one can read the following:
il en est venu à mendier = he has been reduced to begging
Even though the dictionary is not explicit about it, I believe the expression is en être venir à.
If so, does en être venir à mean to be reduced to (something)?
I really hate it when online dictionaries don't make available the proper infinitive-based form of an expression, and their proper, infinitive-based translation into English. For all I know this English translation could simply be a literary rendering of the French original.